I fixed a parasitic drain on my car in 408 days

https://davidmuller.github.io/posts/2023/04/10/how-i-fixed-a-parasitic-drain-in-408-days.html

by dmuller • 3 years ago

466 503 3 years ago

davidmuller.github.io

jws• 3 years ago

I have failed to find the parasitic draw on an RV (slower than this one, it takes a couple weeks to kill the battery). I finally got a "Top Post Battery Master Disconnect Switch", which is a little dinglebob that goes between the battery post and cable and lets you easily break the circuit. I highly recommend the $12 solution for an intermittently used vehicle.

bombcar• 3 years ago

You can also grab a trickle-charger and use that when it's at rest, which can (on modern vehicles) prevent the computer from going nuts.

If you're fancy, you can even make it a quick-disconnect setup so that if you drive away with it still on, it won't break anything (or do the poor-man's version where you have the wire connected to the wheel chocks).

overthrow2• 3 years ago

I thought about this but the problem with newer cars (mine at least) is killing the power wipes the memory so it won't pass an emissions check (or something like that). After my battery died I had to find an excuse to drive an extra 100 miles so I could pass emissions.

On my car the emissions laws definitely caused more emissions than they saved that day.

sidewndr46• 3 years ago

I hear this all the time, but I have never understood it. If I clear my drive cycle monitors, they are all passing again just a few miles later. Do some vehicle manufacturers just put insane constraints on the drive cycle monitors?

ksherlock• 3 years ago

I once had a car where I had to disconnect the battery to clear the check-engine light so it would pass a state inspection.

hirundo• 3 years ago

I installed a battery disconnect switch on the dashboard of my jeep. There's a spot that seems made for it. It was a $27 solution, but I don't have to pop the hood. And it solved my charge parasite problem instantly.

rootusrootus3• 3 years ago

RV

I'm reminded how often people come to the RV forum trying to figure out parasitic draw. The answer almost always ends up being the propane detector. People forget it's even there.

Less of an issue on newer RVs that come with at least one basic solar panel installed from the factory.

pugworthy2• 3 years ago

Probably not an issue with more modern systems with solar panels and the detector on the house batteries.

moffkalast2• 3 years ago

That's one clean burning parasitic draw I tell ya hwat.

driverdan2• 3 years ago

I'm surprised it didn't already have a master shut off switch next to the battery. You should always shut off / disconnect the battery when not in use because, as someone else pointed out, the propane detector will drain it.

dclowd99013• 3 years ago

You really should have one anyway. Good for emergency shutoff.

overthrow2• 3 years ago

Well this is timely. I have a parasitic draw on my NC Miata. The first mechanic just replaced the battery. The second told me it's normal for the battery to die if you don't drive it for 3 days (because "cars have computers now"). It seems like mechanics really don't like digging into the electrical part of the car... but these days that encompasses more and more of what can go wrong.

Without time to dig into it myself I've just been parking it with a battery tender every time I come home.

darrenkopp• 3 years ago

have similar issue with 2011 nissan maxima w/ key fob. guess i have a new weekend project on my hands.

kccqzy• 3 years ago

it's normal for the battery to die if you don't drive it for 3 days

I've heard this nonsense a couple times now. I was incredulous at first but everyone seems to say this. What are anyone's suggestions for a weekend-only car? (I bike to work so I don't need a car on weekdays.) Trickle charge the car battery on weekdays?

stocknoob2• 3 years ago

Or disconnect the battery (you’ll have to reset the clock, etc., which is annoying).

peteradio4• 3 years ago

It's nonsense! If a car is dying after not being driven for several months, ok fair enough. If after several days a particular year make model dies it deserves a recall!

maccard2• 3 years ago

No car I've owned in the last decade has actually drained in a few days. Any car that does has a problem.

_ea1k2• 3 years ago

Yes, they make battery tenders that are specifically for this. They'll trickle charge when needed, but also not charge at all when the battery is at the right voltage.

tadfisher• 3 years ago

You can drive a car from the 90s before they started shipping alarms and keyfobs in every vehicle. My 1995 Miata draws just enough power to maintain the clock in the radio, and it starts just fine after sitting for 6 months (it's not a winter car).

kybernetyk2• 3 years ago

There's battery kill switches you can install onto the battery pole to effectively disconnect everything from the battery. This should work for older cars. For newer ones you may experience hiccups like reverse camera not working for a few hours until it has re-paired itself with the head unit.

tecleandor• 3 years ago

Really nonsense. It's true it might be more common due to all the additional modules and computers cars have now. If one goes crazy, it might drain your battery. But this is only in case of a failure. Edit: cold weather can accelerate that.

If it's 'weekend only', battery should be no problem. If sometimes you leave it a couple months unused, that might be a problem.

Depending on how ready you would like to be when you're going to use it, or the access you have to your car (is it far away or in your garage?) you could add a connector for a battery charger/maintainer (some of them have accessories for plugs you can leave permanently, see the NOCO GC002 for an example), and/or add a battery switch to easily disconnect the battery.

Warning: your radio might ask for a security code if it loses battery connectivity. Be sure you have it.

FartyMcFarter• 3 years ago

I didn't drive my 2019 Mercedes for months during the pandemic and the battery was fine. It did give me a warning when I restarted driving it (I guess the battery was starting to get low-ish), but it immediately fixed itself.

KMnO4• 3 years ago

You should see if there are carshare options around you.

Even if you’re spending $50/weekend (which is a fair amount of driving — Communauto is as low as $3/hr), that’s still quite a bit cheaper than owning a depreciating asset with lifetime maintenance costs (not to even mention insurance and fuel).

heleninboodler2• 3 years ago

Yeah, if a mechanic told me having the battery die in 3 days was normal, I'd stop going to that mechanic.

chrisdhal2• 3 years ago

My wife drives about once a week, probably less on average. She has a 2013 Honda CR-V, only 15,000 miles on it. We live in Minnesota, so have cold temps, but the car in a garage. The car always starts. We've replaced the battery once just due to longevity.

Every 3 days? No way.

rconti2• 3 years ago

I try to keep my cars on trickle chargers (Noco Genius 5 in my case) when not driven regularly, because regularly killing $300 AGM batteries gets expensive.

That said, I'd expect most cars should be able to manage, say, 2-3 months. It's when I exceed 4 months with some regularity that battery life starts getting sketchy.

If you're driving the car every weekend, I'd expect that should be plenty. Note that fancier cars with more electronic features don't do well when only driven short distances. If you only drive 2-3 miles at a time, you might be discharging the battery faster than you're charging it.

aksss5• 3 years ago

Table for reference: https://homebatterybank.com/how-fast-will-a-car-battery-drai...

That said, at between like 0F and -10F, I'd be intentional about starting that car every couple days. Below -10F to -20F, I'd start it each day. Below -20, I'd consider bringing the battery inside for the night - even if you have a battery blanket. Once a lead-acid car battery has frozen, it will die very quickly from then on - I'd believe within a few days or less even in normal weather. AGM batteries are awesome alternatives for the cold weather lifestyle, in terms of their resistance to freezing damage.

Fradow• 3 years ago

That's because it is nonsense.

I have a week-end only car (2002 Mini) and I've had no issue letting sit for a week or two. Including opening/closing it without starting the engine to retrieve stuff in that timeframe.

And a week or two is on the low-end of how much you can let it sit. My SO car (1st gen citroen C3) often don't run for one or two month at a time and there is absolutely no issue with the battery.

On the other hand, if you have parasitic drain and access to an electric socket, there are battery chargers that can keep the car topped up. Or without an electric socket, just unplug the battery when the car isn't used (though that may disable some things, for example in my car the hatch is inoperable without power).

peteradio4• 3 years ago

Mechanics are like doctors: find a good one and be grateful.

rozap2• 3 years ago

It's fairly straightforward if the car is unmodified, as everything should be fused. Multi-meter between positive terminal and positive lead and pulling each fuse to see when the drop goes away will isolate the circuit. Then you've narrowed it down pretty far and can go from there.

The horrible thing is if the car is modified, and you discover an un-fused circuit.

sokoloff3• 3 years ago

I’ve had unknown draws before and many times they’re not constant draws. A constant draw is easy and quick to find. A draw that only happens when some module or other wakes up is a lot harder to find.

everybodyknows2• 3 years ago

Ammeter across the battery terminals and pulling each fuse to see when the drop goes away

How does this compare with the way presented in the article based on measuring resistive voltage drop across each fuse in turn?

mlyle3• 3 years ago

Ammeter across the battery terminals

I know what you're trying to say... but this reads like very dangerous advice and you may want to revise.

Ammeter between a battery's terminal and the car's electrical system.

Also note that you'll probably create sparking when doing this, and if the battery has recently been charging this can be dangerous (hydrogen outgassing).

voldacar• 3 years ago

Ammeter in series, not across the terminals! Unless you are trying to weld something :]

fxtentacle• 3 years ago

Wow. My German car handles being parked for 3 months just fine.

rootusrootus3• 3 years ago

So does my American car.

kybernetyk2• 3 years ago

It seems like mechanics really don't like digging into the electrical part of the car.

If you've ever seen a car's complete wiring harness you'll know why. It's not only because there's three gazillions of wires - they're also heavily insulated with tape that makes it a nightmare to access those wires in the first place.

dylan6042• 3 years ago

there's three gazillions of wires

My old math teacher would deduct points for not listing the units.

mikrotikker2• 3 years ago

As a practicing brochanic angry pixie spaghetti is the worst thing to deal with.

But I've heard so many stories of friends paying hundreds to auto sparkies only for the problem to remain.

lylejantzi3rd4• 3 years ago

It seems like mechanics really don't like digging into the electrical part of the car...

Tell me about it. I'm in a similar boat. My audi a4 has had a parasitic draw for the past 10 years. My mechanic didn't want to take the time to address it because that sort of thing takes a serious amount of time and he's always backed up. I got out my fluke and narrowed the cause to what I believe is the comfort control unit. I can't replace it myself because it's a coded part. My mechanic won't do it because he won't confirm that's the cause.

None of the other mechanics in my area have the equipment. Even the Audi dealership won't touch it because they're backed up too. So, I keep a battery jumper in the glove box and hook the battery up to a tender when I can (outdoor parking).

I don't know what I'm going to do for my next car. Pretty much every car made after 2010 has coded parts and are more computer than mechanical. It does make me tempted to learn the electronics part and open a garage that focuses specifically on fixing electronic issues in modern cars.

addisonl2• 3 years ago

Probably should get a brand more reliable than Audi...

nickff• 3 years ago

The problem with specializing in these issues is that most customers will be dissatisfied when you charge them thousands of dollars to reset a minor module on their car.

How many hours of shop time are you willing to pay for with no guarantee of a solution, and very few (if any) parts replaced?

cwillu2• 3 years ago

If you can identify the fuse for the unit, it might be less annoying to pull it when parking rather than hooking up a charger.

Eumenes2• 3 years ago

I'm looking into buying a reliable older vehicle, pre 2000, and just rebuilding the engine

sokoloff3• 3 years ago

My mechanic won't do it because he won't confirm that's the cause.

My experience is that a lot of independent mechanics will do what you ask them to do, so long as they think it’s not unsafe and have confidence that you’ll pay the bill without complaint when the task is done whether or not the problem is fixed.

Probably not a good “this is my first time meeting you, but please replace my flux capacitor” but if you’ve got a history with the shop, I’m surprised you couldn’t talk him into it. (I worked in a shop briefly in college. We’d do what the customer wanted, including installing parts they bought, but the only warranty was on a “we spent an hour; you paid for an hour; thus ends the transaction” basis.)

sixothree• 3 years ago

Even the Audi dealership won't touch it because they're backed up too.

Getting an appointment at my Audi dealer is always 6+ week minimum wait. I don't think I've ever dealt with a dealer this consistently backed up. And my issues have been recalls and brake problems; but simple oil change is a similar wait time.

JohnFen• 3 years ago

I wonder if installing a switch to disconnect the car's battery entirely would be an acceptable (but obviously hacky) solution.

Nifty39292• 3 years ago

What are coded parts? I spent a minute googling and couldn’t come up with anything that seemed right.

gonehome2• 3 years ago

If you’re going to have to deal with it might as well get a tesla which is at least all in on the electronics and the company understands software.

The dealership model has really been awful for legacy manufacturers.

garyfirestorm3• 3 years ago

I can’t replace it myself because it’s a coded part.

Can you please explain this? Why does it need ‘coding’? It’s not a VIN specific part I’d think - i.e. engine controller. Also have you explored Ross Tech VCDS tool? You might be able to identify the coding on your part and use it on a new part. Replacing an ecu should be straightforward imo.

TheSpiceIsLife• 3 years ago

Have you consulted an auto electrician?

In Australia Automotive Electronician is a trade itself.

A good mechanic should be able to point you to their preferred auto electrical workshop when they suspect an issue is outside their own scope.

99_00• 3 years ago

Everyone should keep a jumper in their glove box.

It's with the price just to see the looks on the faces of stranded motorists you help jump start in one or two minutes after they've been trying for an hour to jumpstart a minivan with a hatchback.

madaxe_again3• 3 years ago

I had similar with my ‘15 Amarok. Battery would reliably be flat after parking for 24h, and I was either told there was no issue or it was unfixable, or I would need a new ECU, a new engine, a new truck.

After a short and inconclusive session looking for leaks through the fuse box, and then many, many hours of crawling around under the truck with a voltmeter, I discovered a frayed and heavily corroded +12v lead associated with the tow harness rubbing against the chassis. Fixed it. Issue resolved.

Unfortunately, a majority of mechanics simply aren’t competent, and the remainder don’t want to touch jobs which are mysteries, as they’ll just end up with a customer refusing to pay.

markdoubleyou• 3 years ago

My last car, a 2007 Acura TSX, had the same problem--it wouldn't start after 4 or 5 days (maybe 2 or 3 during the winter). This model was from the first wave of touchscreens and bluetooth. Mechanics shrugged, pointed to the tiny, underpowered battery, and told me to drive it more.

Thankfully there are a lot of car enthusiast forums out there that have been plugging away on vBulletin for years. Someone on an Acura forum had figured out that the bluetooth module was always on and looking for a connection. I tried disconnecting it, and the problem was fixed.

timlin• 3 years ago

Same problem and same fix for my 2009 Acura MDX.

bhauer• 3 years ago

Same problem with our 2007 Acura TL. And we fixed it the same way.

aksss5• 3 years ago

God bless online car forums. Usually just awesome, well-intentioned, and helpful people that participate, with decades of knowledge indexed. There was a year way back there when the usefulness of the forums surpassed the Chilton's manual for me entirely - probably something to do with the addition of YouTube.

brewdad• 3 years ago

Don't ever go back to that second mechanic.

alexchantavy• 3 years ago

I saw this on the Gears and Gasoline Youtube channel: https://youtu.be/XgOowUWbCdk?t=628 -- looks like a lot of work to trace a parasitic drain.

jeron• 3 years ago

If you like watching amateur YouTubers rip out their hair chasing electrical problems, I recommend checking out Tavarish and Samcrac. It turns out cheap flooded auction cars have tons of those

scrlk• 3 years ago

It seems like mechanics really don't like digging into the electrical part of the car

Probably worth taking it to an auto electrician, rather than a mechanic.

ilyt6• 3 years ago

At the very least you know to which 2 mechanics you should never give your car to

bityard5• 3 years ago

It seems like mechanics really don't like digging into the electrical part of the car.

That is certainly correct. Troubleshooting electrical issues takes a different set of skills than most mechanics are trained to deal with. Most mechanics are so busy that throwing parts at a problem is the best way to deal with issues where the cause isn't readily apparent. It's not worth their time to really dig into a difficult issue because if they spend 8 hours of shop time and try to bill that to a customer, the customer is going to just balk anyway. Better to throw a part at it, bill 1.5 hrs, send it out the door, and let the next guy deal with it. And then move on to some more profitable muffler and brake repair jobs.

This is thankfully not ALL mechanics, but it certainly is a large percentage of them, IMO. (Yep, even dealerships.)

amtamt• 3 years ago

This sounds like a majority of software engineers (and their direct managers) asking to add more CPU and RAM, when software is slow, instead of analysing a problem.

I guess mechanic's time is more valuable than parts.

explaininjs• 3 years ago

In the military, the folks tasked with Mechanical maintenance of vehicles are an entirely different branch with different training, infra, etc than those tasked with Electrical maintenance of vehicles. Perhaps we need a similar dichotomy on the civilian side.

legitimayzer• 3 years ago

It seems like mechanics really don't like digging into the electrical part of the car.

this is like saying that computer programmers don't like digging into the proprietary and binary blobs from other vendors.

I am trying to say it's not fair to blame mechanics because even if they want to dig into the electronics, the car manufacturers take active measures to prevent 'random mechanics' from digging around.

I suppose there are many rational and reasonable way to justify why this is so; probably all having some form of "because safety" and "because IP of vendors".

jerrysievert2• 3 years ago

3 days is definitely not good for an NC. That said, mine is usually around 2 months before the battery is drained. That should give you some better expectations.

sterwill• 3 years ago

2006 NC owner here with a reasonably new battery. I keep it parked in an attached garage, so no extreme cold or heat. Mine will always start after leaving it for 1 month. I probably left it for 2 months at some point in the last two years, and it started, but that feels like pushing it.

The next time a mechanic tells you cars can't sit for a few days without a battery drain problem, ask how people who park at the airport get home after a two-week trip.

micromacrofoot2• 3 years ago

I've been to multiple mechanics, talked to roadside assistance people, posted in multiple forums, and talked to family about this problem with an old car of mine... and they all swore up and down that you should start a car if it sits longer than a weekend, maybe a week tops. They made me feel insane about it, it's one of those widely accepted things that's just not true most of the time.

jollyllama• 3 years ago

There are other reasons to do that unrelated to the electrical system of the car. You're keeping the engine and any other moving parts lubricated. You're burning fuel, so that you don't wind up with as much degraded oil.

Dave_Rosenthal• 3 years ago

I think a cheap thermal camera would be very helpful in these situations with a relatively fast drain. A car battery is ~1 kWh so anything that drains it in a few days is dissipating on the order of 10 watts. In my experience that's very easy to see in a thermal camera. Just leave the car in a nice thermally-stable place for a day and then go hunting.

mattbrewsbytes• 3 years ago

Imagine as a software developer you tracked your time working tickets, your pay was hourly, and depending on the ticket type you were prescribed how long that ticket should take and paid those set hours whether you went over/under the set hours. This sounds completely insane but this is how car mechanics work (as I understand a lot of shops do this). Replacing a battery might be 1/4 hour labor, replacing brakes on car model XYZ is 1.25 hours, etc. This is why mechanics won't really want to spend time on issues like this. It could be a wild goose chase tracking down every electrical sub-system in the car only to find something chewed thru a wire somewhere under a panel. The fix might be $15 in parts and 20 hours of actual labor but their system might quote replacing a wire as 1 hour labor.

winrid• 3 years ago

That's kind of how dealer mechanics work but not any other mechanic... They work for 10 hours, you get billed for 10 hours.

pengaru• 3 years ago

It seems like mechanics really don't like digging into the electrical part of the car... but these days that encompasses more and more of what can go wrong.

Having worked as a mechanic in my youth, and worked as a software engineer in SV, the kinds of troubleshooting skills and detail-oriented attention span involved in diagnosing these issues are far more common in the latter than the former industries.

My impression is it's rare for someone with such abilities to stay a mechanic, they can earn far more money in tech, with less exposure to hazards.

On the subject of mechanics failing to diagnose electrical issues, I have my own story too:

Decades ago, back in IL, a friend inherited a low-mileage minimalist Ford Escort hatchback, manual trans, crank windows, it was a great little econobox to inherit, on paper. He kept having the battery die on him. Not being a mechanic or even a hobbyist gearhead himself, he kept bringing it to shops. They replaced the alternator, the wiring harness, the battery, the starter, they just kept throwing parts at the car. This is what most "mechanics" do nowadays; a poorly informed process of elimination via new parts, on your dime.

I hadn't been in contact with this friend for years when I heard about this "cursed" low-mileage car sitting in his garage, full of new parts with invoices totaling well over $1k. He was car-less at the time because of this situation. I offered to fix it for him, but he didn't have any confidence left in the vehicle or my ability to fix it, he was understandably fatigued by the whole thing. So I offered something like $250 and took the car off his hands.

15 minutes with a voltmeter revealed a huge voltage drop across the negative battery terminal and the chassis. Followed the negative strap to where it attached to the chassis and the area was corroded (recall it's an IL car). Removed the rusty bolt, wire-brushed the unibody steel behind it, the bolt and cable lug, slapped dielectric grease on everything and reassembled.

The car charged the battery fine and ran like a champ. I ended up selling it back to him a year or two later for basically what I paid plus a few hundred for my trouble/towing etc. He wouldn't even take it back until I had driven it for years to prove it was fixed. It was that brutal an experience for him, dealing with "expert" "mechanics" bleeding him dry.

jseutter• 3 years ago

Eric O from the South Main Auto youtube channel has some great videos on tracking down parasitic drains on modern-ish cars. From his videos I learned that often cars won't fully sleep for up to 45 minutes depending on the model and manufacturer, as well as checking for the voltage drop across fuses to figure out which circuit is draining the battery. With this I was able to track down a parasitic drain in my 2000 Beetle (failing door lock). I'm sure he mentioned other tips as well but those are the ones that stick out to me.

bonestamp24• 3 years ago

The second told me it's normal for the battery to die if you don't drive it for 3 days

No, this is not normal. When the cars are manufactured, they often sit for more than 3 days just to get on a train for delivery. During transport they often sit for more than 3 days.

oliwarner• 3 years ago

mechanics really don't like digging into the electrical

Mechanics don't like fishing expeditions for nonessential things. $100/h for 2+ hours diagnostic, followed by tedious parts to replace and pair up.

A new battery every couple of years and a trickle charger probably seems like better value to them.

dd36• 3 years ago

I solved one recently. Really wish there was a simple time logging multimeter that you could leave plugged in 24 hours.

nikau3• 3 years ago

Most cheap multimeters have an ir or similar data port you can use for that.

Just need to hold a button when turning on the meter to disable the auto power of timer, then you run software on a laptop to log the data to csv

rootsudo• 3 years ago

Heh, I also have an NC2 Miata, and I don't drive it for 3-6 month periods, and it still starts on the first/second engine spin.

If the battery is over 3 years old, I would replace it and start anew simply because of the life/abuse it'd had so far.

And then I'd start at the obvious ones - radio, aftermarket radio, alarm, etc. You can literally put a multimeter along the fusebox to see what is pulling voltage after - but most likely it will be something along 12V connected switch.

Wiring isn't problematic, but if you have a hitch installed it may be wired to always be on.

lukevp• 3 years ago

I also have a parasitic draw on my NC Miata, and ALSO use a battery tender every time I park it! If you find out the issue, let me know, would be interesting to see if it’s the same!

aivisol2• 3 years ago

For my VW van it was alternator - one of the diodes in the rectifier was obviously blown and leaked current backwards.

xeromal• 3 years ago

I'm sure if the mechanic was paid for it hourly they'd gladly tear your car apart trying to find the drain, but I think most people can't stomach that.

If anyone takes a car to a mechanic and asks for the estimate and the estimate is (100$ an hour until I find the leak and it may take a whole day or two), then most people are gonna gag.

You need to find an expert in your car.

iKlsR• 3 years ago

For me it lasted close to 4 years. I had installed a tracker that uses a SIM that you have to keep topped up to receive the messages. No issues where I live so over time I stopped and didn't even think about it. Fast forward, I went through 3 batteries, couple mechanics, bought a portable jumper and a physical battery disconnector and even got a voltage meter and was mucking around with the fuse box etc and just grew to live with it until one day I was cleaning the car, saw the thing and just disconnected it and then a few weeks later I noticed that leaving the car on weekends the battery was fine the Monday (usually had to jumpstart as it would drain). Turns out the tracker was trying to send messages almost every minute THAT it couldn't send messages! So it had been doing that for years and was the tiny leech on the battery, not large enough to be detected but enough to slowly drain a brand new battery over the course of a few days.

bouke• 3 years ago

I once had a parasitic drain on my BMW 3-series (e46). The dealership diagnosed the problem appropriately. It turned out to be the GROM Audio module I installed to replace the CD changer. It would drain the battery in about a week. So back to burning CDs and the issue was resolved.

jonmb• 3 years ago

Our 1990 Miata has a parasitic drain too. We installed a battery disconnect switch that takes about 5 seconds to connect or disconnect whenever we use the car. It's a little bit of an extra hassle, but it was an easy solution.

sh34r3• 3 years ago

Let me translate the second mechanic's advice into our language: "Have you tried turning it on and off again?"

How much of your clients' time (and therefore money) would you spend chasing down a bug in software with an unknown root cause, which never appears as long as operations schedules a restart every couple of days? Software engineers are all too happy to dive into those rabbit holes, but that's because we don't usually have to look working stiffs in the eye and hand them the bill for our services.

That's likely not an incompetent or lazy mechanic. It's an honest one who doesn't believe they can solve your problem at a price you'd accept.

The first mechanic, on the other hand, I'm a lot more suspicious of. Did they bother testing the battery before replacing it?

blobbers2• 3 years ago

Is it possible the key fob just needs replacement and is causing the intermittent sleep failure?

leviathant• 3 years ago

That's probably what the author was thinking in February 2022 when they removed the batteries from their keyfob and only used the metal backup key, only to have the problem resurface less than a year later. It's probably safe to say that without batteries, the fobs were having no effect on the keyless system housed within the car.

instaclay• 3 years ago

I was also curious about this.

Maybe the keyless entry computer stays awake to try to sync with a fob and then sleeps on success? If a user chooses not to use a fob at all, maybe it stays awake indefinitely trying to find a key to sync with.

Captaffy2• 3 years ago

From my own experience I believe the issue is that when these modules start to go bad they fail to turn off and stay awake indefinitely.

blobbers2• 3 years ago

Yeah sleep-wake problems often are related to things missing or broken in the (poorly constructed) system.

If the software on the car was poorly written, it may not have had a good back-off on the fob check, or if the fob itself was malfunctioning it may have left the car in a weird state.

While I wouldn't expect a fob to drain a car, it certainly doesn't seem implausible, especially given what the fix is.

fullstop2• 3 years ago

Thinking this through a little bit further, I am wondering if subsystems can wake up if someone else uses their fob but the key signal doesn't match. Surely, at some level, something has to wake up to validate this.

sixstringtheory3• 3 years ago

Back when I was commuting there was an older subaru I always parked near in the parking garage that, whenever I unlocked my newer subaru with my fob, it’s alarm would go off. I sat there one day and did it over and over again, so it was definitely casual.

buescher• 3 years ago

My conjecture: there is ambient RF noise on key fob's frequency (most likely 315MHz), which is causing the key fob receiver circuit to remain active and process any signals that it receives, rather than going to sleep and periodically waking up to check for incoming transmissions.

Captaffy2• 3 years ago

Had the same problem recently with a 2011 Mercedes. Didn’t figure it out until eventually the Keyless Go module (which allows push to start and automatic door unlocking) died. This fixed the parasitic drain.

Apparently when these sorts of modules are dying they fail to turn off and drain the battery by constantly searching for the key fobs. Incidentally while the battery drain was going on the key fob batteries were dying extremely quickly as well, also suggesting a lot more communication than normal was occurring.

1970-01-012• 3 years ago

Intermittent car issues are the worst! Related is the 'My car hates vanilla ice cream' story:

https://web.archive.org/web/20060213052358/http://www.campbe...

netsharc• 3 years ago

Maybe I've read this before, but I guessed by the problem description that the answer probably had something to do with time...

teddyh• 3 years ago

That’s an old urban legend: https://www.snopes.com/fact-check/cone-of-silence/

localhost• 3 years ago

While not a fix for this problem, a nice form of insurance is a Lithium Ion jump start battery[1]. I'm amazed that a hand-held battery can discharge fast enough to jump start my car, but ... it works great.

[1] https://www.amazon.com/dp/B0B55RFM1Z

tokamak-teapot• 3 years ago

Might the battery charge a capacitor?

tvarghese73• 3 years ago

Yeah she had one of these too.

ceautery• 3 years ago

This is type of thing I've seen Eric O. over at South Main Auto[1] fix in dozens of videos. Mad troubleshooting skills, works hard to find root causes of things. He's pretty amazing, hidden away in some no-account town in upstate NY.

1 - https://www.youtube.com/@SouthMainAuto

gooseyard• 3 years ago

I really enjoy his channel- another good one is the Pine Hollow Auto Diagnostics channel, which has dozens of really involved parasitic draw diagnoses, have learned a great deal from that one.

bityard5• 3 years ago

Although I perform as much of my own auto maintenance as I can, I watch Eric O because he's entertaining, and all of the technical wisdom and advice just comes along for the ride.

ldoughty• 3 years ago

Man, I would love for him to look at my 2003 Ford Ranger. I turned on the headlights and the anti-lock breaks engaged and the gauges randomly fluctuated. That's the most recent 'fun' story I have with it... Had a parasitic drain in this thing for 5+ years, but it operates 100% fine as long as I keep the battery charged with a tickle charger and can avoid jumping it. I've mentioned this to nearly every mechanic in the last 5+ years, no one has ever found the issue. Three said replace the battery, 1 said get a new alternator. Seems like those 2 would be the go-to for mechanics these days.

1970-01-012• 3 years ago

Check your ground wires, especially when you flip the light, honk the horn, or anything that is relatively high current. Corrosion on a wire can be fixed with Deoxit spray.

mysql• 3 years ago

I used to be a computer engineer working on embedded systems for automobiles. Quiescent current is what the normal proper draw is called for these systems when the car is off. We worked very hard getting these numbers in spec but it was hard to catch everything especially in this case where the issue is probably due to software missing the sleep state for that module. This could be from bad code or your CAN/LIN bus is messed up in your car. 99% of mechanics (and engineers) have no idea where to start with debugging these issues and the answer will be "replace the module".

xattt2• 3 years ago

This could be from bad code or your CAN/LIN bus is messed up in your car.

If the car had been operational for years and years, why would bad code crop its head now?

toast02• 3 years ago

Some counter finally overflowed. And now the new value is less than the old one, which breaks something, etc, etc.

everybodyknows2• 3 years ago

Anecdata: Some Hondas (e.g . 2010 Element) exert enough parasitic drain to put the car into a chronically undercharged state if a door is left ajar overnight.

The wrong thinking turned out to be: Car is safe in garage, interior lights go off, and my hands are full now -- why bother going back to the door to shut it completely?

porkbeer2• 3 years ago

Never seen this issue with any hondas, including elements, sure you got a good battery? But leaving a door ajar is user error.

depingus• 3 years ago

Thanks for this timely post. I'm literally in the middle of running down a parasitic drain on my Nissan Xterra.

I tracked mine down using a different method which helps when your fuses don't all have test points (and no conversion table needed).

- Disconnect negative battery cable

- Switch your multimeter to 10A (don't forget to swap lead ports)

- Connect the multimeter in-line between the negative cable and negative battery post

- The readout on the multimeter should now tell you how much drain you have

- Start pulling fuses one by one until you see the amps drop to normal

Scoundreller8• 3 years ago

And pro-tip if you need to go down the line past the fuse box: if you have a DC clamp-on ammeter, you can do multiple windings to 2x or 3x the current readings for smaller draws that the clamp-on might not pick up on.

justnotworthit• 3 years ago

Whoa, thank you. I was disappointed to read in my multimeter's manual (klein CL800) that the resolution for DC (up to 60A, if I'm reading "range" in the chart correctly) was only 10mA.

vivalibre• 3 years ago

There is a YouTube channel that has a lot of excellent content on finding and fixing parasitic electrical draws. Pine Hollow Auto Diagnostics.

nb: I am not affiliated with this chan, just a fan.

benatkin• 3 years ago

He should move to San José.

insane_dreamer• 3 years ago

Dealer: said my car was fine and returned it to me. My car died the next morning.

Least surprising finding

ciscoriordan• 3 years ago

I had a parasitic drain on my Tacoma from my Automatic device (OBD-II reader / GPS tracker). I parked in a garage with no cell service and it drained the battery by constantly trying to connect. It was a non-issue when I commuted daily but started killing the battery when COVID happened and I switched to WFH.

Hard for mechanics to diagnose because they had no idea what that device was and also one of their first steps was to unplug it, put it in a cupholder, and plug their own OBD-II reader in.

Now the Tacoma is parked again most of the time because I got a Tesla and I'm noticing a voltage drop. I need to do more research, I don't know if this is normal for being parked or if there's a drain.

karolist3• 3 years ago

My father (a professional auto mechanic) took about 6 months to find a random engine shutoff during harder cornering in his Toyota, the culprit was a damaged inner insulation layer for a few wires within the wrapped wiring harness for the ECU, engine moving on the engine mounts would sometimes cause a slight harness shift and a short would cause a hard reset of the ECU.

Another story I have is my computer geek friend finding an issue with my Subaru Legacy, when no other mechanic could (I tried 3). The issue was that the car was old, first gen OBD, he downloaded some legacy asm ECU reader and made a diagnostic cable from spare parts, the issue was that the car would not start when cold, or be extremely hard to start. The culprit was damaged wire that tells the ECU that the engine is in cranking condition, therefore needs a different fuelling mode, without seeing this mode there was not enough fuel to start when cranking. Eventually this was found by hooking up an oscillograph to see the injector impulse length (duty cycle), as the old gen. diagnostic didn't show any errors, he compared a working car injectors to mine when cranking cold and found this. 10 years later I'm still amazed by his skill and dedication, I'd have scrapped the car otherwise. The car was sold eventually to another person who restored it (rust repair mostly) and his wife still drives it to this day, a 1994 Subaru Legacy.

ryandrake2• 3 years ago

Your friend’s fuel issue seems a lot like the intermittent no-start, low fuel pressure issue I have been debugging (3-series) for over a year now. It has defeated three dealerships and two independent mechanics so far, so I’m taking over the diagnosis now. No clue yet but today’s cars have too damn many computers in them.

karolist3• 3 years ago

which engine is that? I had an N54 335 for 5 years too, even E36 era BMWs have vastly superior error logging compared to JDM from that vintage. I hope you find your issue, but if it defeated dealerships it sounds troublesome. Log some live data with INPA if it's an older one, I have no experience with BMWs post EXX series to drop any advice...

Spare_account2• 3 years ago

Take a look at my other comment

https://news.ycombinator.com/item?id=35516985

Spare_account2• 3 years ago

This methodical approach to vehicle diagnostics is something you can see on YouTube at South Main Auto Repair

https://www.youtube.com/@SouthMainAuto

Eric regularly takes the viewer through the entire process including sometimes measuring electronic components with diagnostic tools that include oscilloscope functions.

PuffinBlue• 3 years ago

Pine Hollow Auto Diagnostics goes even deeper. And focuses much more on the diagnostic. These two channels are good together in that they show different sides of the auto repair industry.

Ivan has done some parasitic drain diagnosis in the last few videos, including a new custom made logger that he had sent to him for tracking drain over long duration (like overnight or a couple days).

If you like South Main Auto and you havent' seen Pone Hollow Auto Diagnistics, I think you'll like it.

https://www.youtube.com/c/PineHollowAutoDiagnostics

makerdiety• 3 years ago

Skill and dedication indeed. The cost of being able to determine the root cause of the car problem probably costs more than the car itself. By a factor of ten.

djmips2• 3 years ago

That's a nightmare and sounds like a really bad software bug... I have one like this even as we speak.

zwieback2• 3 years ago

Not just for highly computerized cars, I have a 97 Ranger where literally everything is manual and I don't even have a dome light anymore. There's a parasitic drain I can't quite figure out so I just make sure to start it every once in a while. Since I'm a year round bike commuter the truck can sit around for a long time, especially in winter when there's no house and garden projects. I've considered adding a manual battery disconnect, the only thing I'd lose are the pre-programmed radio stations.

Scoundreller8• 3 years ago

Solar panel? Depends how big the draw is.

zwieback2• 3 years ago

Good idea, solar panel for trickle charge. Could power a few other things like a wildlife cam and weather station.

rapjr9• 3 years ago

After the pandemic started I was using my car about once a month or two and the battery was getting drained enough that the car would not start. This solar panel fixed that problem:

https://www.amazon.com/gp/product/B07Y5TKMZ4

It is powerful enough to actually charge the battery instead of just maintain it, and it has a charge controller so it won't overcharge the battery. It did fail me once when we had a couple months of rain and overcast weather, but kept the car going otherwise. Eventually replaced the battery with an AGM battery and that plus the solar charger has worked very well.

mbfg• 3 years ago

South Main Auto has an excellent youtube channel with various parasitic draw videos. For those struggling, it's a good watch.

Here's one such: https://www.youtube.com/watch?v=qDqlG5bRq8k

rrmm• 3 years ago

Second this suggestion for anyone working through parasitic draw issues. He has a very solid, logical process for working through this (among other issues). I always enjoy watching the videos because it's like watching a who-dun-it where you're trying to guess the cause as he gathers evidence.

Gordonjcp• 3 years ago

I found that my old (1997) Range Rover would flatten its battery after being parked outside my house over a weekend. If I didn't drive it for two or three days, it would be too flat to start.

It turns out that the BECM (body ECU) wakes up from sleep if it hears anything coming in from the RF keyfob receiver, on 433.92MHz, a standard ISM frequency. If it's not a valid fob code (and there is a surprisingly complex rolling code sequence) it'll go back to sleep after 20 minutes or so.

The oil tank gauge for my central heating had a remote sensor that... yup. Transmitted on 433.920MHz, of course.

The aerial for the keyfob is on the rear right corner of the vehicle, the oil tank for the heating was on the left-hand side of the driveway right at the back of the house, so when I backed into my driveway it was right beside the receiver.

I managed to do just fine with popping the lid off the oil tank once a month and looking inside to see how much fuel was left, having taken the battery out of the tank sender.

83• 3 years ago

Can't recall where, but I recently learned this was a common issue at airports in the early days of wireless key fobs. The radar sweep at the airport would wake up the receivers causing cars parked there for a while to have dead batteries.

nuancebydefault2• 3 years ago

Once you find the fuse that passes the highest current, why not just place a switch button in series with it? Turn it off when exiting the car. Add an LED to show when it is on.

falcolas2• 3 years ago

Personally, I'd go for a relay on a non-problematic circuit.

But I also get why you might just leave it disconnected - if it's pulling a few more amps with no clear cause, what is going to go wrong with it next, and what vital system will it take with it?

nuancebydefault2• 3 years ago

Oh a relay that goes on after you turned the key would be very handy. It is rather easy to find a point where there's only a voltage present after/while starting.

Of course, when the array controlled circuit would be vital for entering or starting, this would not be an option.

Scoundreller8• 3 years ago

If you’re going to do all that, just rewire it so the circuit only turns on with key-on.

tvarghese73• 3 years ago

It was not all that easy to get to and not all that easy to mount a switch securely near by. May be I just lacked imagination.

The real reason and the part I skipped was the leakage current was getting worse over time. By the time I replaced the MICU it was close to 2A draw. It was just a matter of time before it died.

binkHN• 3 years ago

Had a similar issue with a 1.5-year-old vehicle that would have the battery fully drained in a little over a week if the vehicle wasn't driven. Had the dealership "fix" the problem three times and the problem was never fixed. I used the lemon law to get a brand new vehicle. I won't name the brand, but dealing with the manufacturer for this was rather trouble free.

sizzle6• 3 years ago

Name and shame, help your fellow HN readers out, no shame in getting a lemon!

arscan2• 3 years ago

Wow, I have a 2012 Mazda3 and have the same problem, which only really surfaced during the pandemic when I stopped driving my car regularly. The dealer said it was just a normal level of drain (even though it would die in just 4 days of non-use) and I should get a trickle charger. Which I did, and is annoying, but is something that I can deal with. I’m not sure if I’m willing to disconnect my remote entry to see if this fixes it, but I’m glad others have seen similar behavior because it really bugs me that the mechanics would just shrug and not really diagnose why this was happening.

williamDafoe• 3 years ago

We have a similar problem with a Lexus rx300 2001. The computer never goes to sleep. I was thinking of looking for (or making) a patch-fuse with a kill switch to stop the drain. Computer sleep depends on the flakey door controller switches.

bruiseralmighty• 3 years ago

My current driver is a pre-2010 vehicle. I really don't want to buy any of these newer cars. Maybe I can import one from Cuba.

maherbeg• 3 years ago

Well this is entertaining. Our 2012 Mazda CX-7 seems to die if we don't drive it for a week. I've sort of ignored this problem but now I'm going to go check some fuses and see if this is the same problem.

KingMachiavelli• 3 years ago

I've never understood why cars don't just cut power before the battery is too low to start. If that's too complicated then just have an option to cut all power after X hours of non-running time.

I bet the old popular theft of car radio is a root cause; cars needed to stay running to keep the alarm active and power the radio continuously so it wouldn't require the unlock code every time you start the vehicle.

It's actually pretty impressive how much power even a 200mA draw at 12V is over a few days; it's about 58 Watt-hours or 3.5 iPhone batteries per day.

topspin2• 3 years ago

I've never understood why cars don't just cut power before the battery is too low to start.

The design of most cars can't tolerate losing 12V DC power without problems. Clearing superfluous codes after a battery swap is SOP. Cars are build for two simultaneous customers: regulatory regimes and work-a-day 13.5K miles a year workers that start (and thus charge) their cars at least every 48-72 hours. Other use cases aren't really considered.

Some are better than others though. I have a 21 year old Nissan with a factory alarm and key fobs that sits for a month or more and starts fine every time. Heating helps a lot.

topspin2• 3 years ago

Something I forgot to mention here that supports my view that designers of modern cars are not thinking about this problem at all: after battery power is lost cars lose their maps and tables for ignition timing and fuel delivery. After a usually short period of time (20 minutes is typical) that data is lost and the engine etc. has to 'relearn' when the power is restored and the vehicle is operated for a time.

pvaldes4• 3 years ago

why cars don't just cut power before the battery is too low to start.

Some cars computers block the start by software if the battery is "slightly" low (even if would not be too low to start).

bonestamp24• 3 years ago

Cutting the power is easy, the hard part is for the car to know when/how to reconnect power when the driver wants to start the vehicle. I guess with a physical ignition switch, the mechanical motion of the tumbler could reconnect power. But, most cars don't have ignition tumblers anymore.

fullstop2• 3 years ago

"Fixed" in the same way I can "fix" a stuck key on a keyboard by physically removing it. They've circumvented the problem but are left with less than what they originally had.

bonestamp24• 3 years ago

Ya, keyless entry/start is a huge convenience. I'd be mad if I had to disable those features to use my car.

d3ad1ysp0rk• 3 years ago

I was hoping he'd take the module out and open it up to see what was fried/malfunctioning inside.

Lord_Zero• 3 years ago

Had to scroll down pretty far to find this. Author uses the word "fixed" everywhere but didn't actually fix anything. They just lost a feature of their car they no doubt paid quite a bit extra for on the bottom line.

jimmytucson• 3 years ago

I had a similar problem with a Silverado. It is very annoying. When WFH started and I stopped driving every day, I had to jump the battery seemingly at least once a month.

I had people tell me it was the battery - I knew it wasn't because I had replaced the battery a few times due to the parasitic draw emptying it over and over and wearing it out. I took it to a trusted mechanic and they told me they didn't want to fix it. I pulled all the fuses myself, one-by-one, and never figured out which one was the problem.

legitster3• 3 years ago

I feel pretty handy with car repair stuff, but "intermittent electrical problems" are the absolute worst. In this case they were pretty lucky to trace it to a specific module. You have miles of cables in a car and and most of them are completely inaccessible. There are never any fun, happy, clever troubleshooting stories. You always feel robbed of your time.

This isn't a new problem either - ask anyone who tried dealing with a British roadster. It's also why I stay far away from used cars with aftermarket accessories.

grokx• 3 years ago

In the 00s, my dad had an issue with the infotainment system of its Peugeot 407 that would no longer boot.

An official Peugeot mechanic told him that it would cost something like 4200€ to replace the unit, so he asked me if I could have a look.

After a quick search, I found an update for his system, burn it on a CD, and put the CD into its car.

The system updated, and then would work normally. Problem fixed for one hour of my time and a CD.

Scoundreller8• 3 years ago

A lot of dealership mechanics are mindless flowchart followers that aren’t even allowed to use their brain.

Though I’m surprised “update” wasn’t a part of that official flowchart.

Have had dealership mechanics ignore my notes and identify a part as being failed despite my method of 100% excluding that part as being bad.

porkbeer2• 3 years ago

Theybare because they are trained to be. You are actively dissuaded from any diag work, because it can be harder to justify your hours to the customer and dealerships are awful. For a mechanic, its a good and bad job. Nevermind ASE certification that encourages the same. Only small indie mechanics have the freedom to do good work.

sixstringtheory3• 3 years ago

Hah. I’ve replaced the battery in our Subaru Outback on average once per year, which is way too high for this environmental minded person.

I just went out last night to grab something from the car and it was making a loud electrical whirring noise. I had driven it several hours prior, no idea how long it had been going. I recorded a video and it is clearly audible. I started it and turned it off again, and the noise stopped.

Friend of mine (and several other commenters here) has an old pickup with a switch on the steering column that cuts the circuit at the battery, I’m ready to install one on both my cars.

anamexis• 3 years ago

Ugh, I've also got an Outback (2019) with a regularly dying battery. Let me know if you ever find any leads on the root cause.

sixstringtheory3• 3 years ago

One was a PEBCAK that I personally consider a design flaw: the rear gate light switch is on the ceiling at the opening of the gate (on our 2016), and the “on” position is activated by moving the switch outwards, ie towards the back of the vehicle. It had been inadvertently dragged into “on” position while unloading bikes, rafts and other outdoor gear, and then killed the battery while we were out for a couple days.

Didn’t realize this was happening until returning to a drained battery on two occasions, and then observing the effect later while doing some garden work, when I finally connected the dots. I’ve since duct taped it into the “off” position.

ninjanicely2• 3 years ago

I have a 2019 Outback as well. I just went through some battery dying issues. Took it to the dealership, they said that the Onstar module (after 2-3 years) will start to malfunction and create a parasitic drain.

The only fixes they have (as of a couple weeks ago) was to a) buy a new module (which are on back order because a number of peeps are having this problem) -- which will eventually break because they haven't reengineered it. b) disconnect the Onstar module via a circuit (my tweeters are on the same circuit, so I'd lose them) c) Open up the center console and only disconnect the Onstar module.

I opted for C (which I was charged an hour of labor for). The tech there said to check back in every few months to see if Subaru puts out a new module that fixes the issue.

Edit: The tech told me the Onstar module was a specific issue with 2019 Outback/Legacy, and that 2018 and back doesn't have that problem and in 2020 they redesigned the whole model, so the newer ones don't have that issue.

sevenf0ur• 3 years ago

I would check your owner's manual. Mine says not to be alarmed about noise coming from under the truck. In my case it's a fuel evaporation check.

wisosim• 3 years ago

That whirring noise is likely from the EVAP system of your Subaru. See below threads for more info about it. Having to replace your battery once per year is not normal though so there is definitely something else going on.

https://www.clubcrosstrek.com/threads/buzzing-sound-from-pas...

https://www.subaruxvforum.com/threads/whats-that-sound.14672...

jakestl• 3 years ago

Same here, 2018. Last battery replacement was 6 months, let's see how long this one lasts.

aftbit2• 3 years ago

I have a parasitic draw on my 2004 Honda Civic back in college. All the mechanics I went to wanted to sell me a battery or alternator. I finally bought a meter with a 10A current limit and tested every fuse each time I parked. It turned out to be an issue with the magnetic AC clutch, so I drove it for 2 more years with the fuse for that component removed.

bonestamp24• 3 years ago

In hindsight, you could have put a relay on that circuit that was powered by some other circuit... so it only connected the AC clutch circuit when the vehicle was on.

aftbit2• 3 years ago

Yeah that would have been smart. What I did instead was just drive with the windows down. :) When it got too hot, I put the fuse back in, kept a jump pack in my trunk, and parked on a hill so I could pop the clutch to get a start.

antiquark• 3 years ago

I solved this problem on my Dad's car by installing a mechanical knife-switch on the battery terminal. Anytime it's going to be parked for more than a few days, I pop the hood and disconnect the battery.

civilized2• 3 years ago

My wife and I gave our old car to her parents. In the subsequent years, its battery kept dying and we had to go over to their place and jump it. Never happened in the prior 7 years we'd owned the car. The mechanic said nothing wrong with the battery, but suggested there might be a parasitic drain somewhere.

A few days later, we were visiting them. I looked at the car and saw the door closed, but not properly latched and ever-so-slightly ajar. You know, that half-closed thing car doors do when you don't close them hard enough.

It turns out someone, possibly my son, had been not closing the door completely. This did not keep the lights on or cause any other visible sign, as it would in some cars.

After I told them to slam the door fully shut, never a problem again for 2 years and counting.

WirelessGigabit2• 3 years ago

My car beeps loudly and angrily at me if the doors are not 100% closed when I hit the close button on the fob.

gengkev• 3 years ago

With my car, trying to lock the doors just doesn't work if one is left open — not always the most obvious failure mode, but it's been enough to get me to notice something's wrong.

djmips2• 3 years ago

Horrible.

sundvor• 3 years ago

Mine auto locks/unlocks, and will message me as I leave it if I left it ajar.

adversaryIdiot2• 3 years ago

Thats insane... To consistently not close the door like that

civilized2• 3 years ago

I know, I'm at a loss. The kid slept in there a lot - maybe they were trying to shut it quietly to not disturb him?

o10449366• 3 years ago

My wife, bless her heart, leaves everything partially open. Not even just open, but she'll screw the lid on jars just enough where if I pick it up by the top they'll drop. It drives me crazy.

mrtnmcc• 3 years ago

Thats insane... To consistently not close the door like that

It sounds like it happened occasionally causing the battery to drain overnight. So not necessarily improper close every time, but a dice roll.

Dalewyn• 3 years ago

Tangent, but what's the rationale for car doors requiring slams? They are the only door I know, at least in common, daily life contexts, that require slamming them with the force of Thor to properly close them.

noizejoy2• 3 years ago

I think one of the reasons is air pressure inside the car.

I've always found it amazing how much less slamming the doors needed when a window was left wide open and the air inside the car could escape freely.

thereisnospork• 3 years ago

The solidness is an indicator of quality. Apocryphally Mercedes used to add lead weights to their doors to get that solid 'thunk'. Nowadays car manufacturers are a little more subtle at it -- there's a lot of engineering that goes into how a car door feels and sounds to give that impression which is very much intentional.

King-Aaron• 3 years ago

They rarely require a slam. You can soft-close the door, then lean on the outer edge enough to engage the latch.

Often, the door just isn't aligned correctly. Either it's sagged on it's hinges over time, or the latch itself needs a minor alignment/adjustment (Note that even on a lot of new cars, this still helps a lot! Not all manufacturing is perfect). Other times the rubbers can be hard and perished and it doesn't allow the mechanism to engage properly.

dTal2• 3 years ago

At a guess it has something to do with needing to withstand 70+ mph winds. There needs to be considerable force holding the door against its seals at all times, and in a mechanical latching system this force must come from a spring, which must be charged with energy via a good slam.

However there are minivans with electronically operated sliding doors, which either power the latch allowing you to gently close the door, or (going further) powering the entire closing operation at a button push. I surmise the reason we see it moreso on minivans is because 1) it is particularly difficult to work up enough energy to properly latch a sliding door, due to losses from the 90-degree change in direction at the end, and 2) violently slamming the sliding doors on a minivan is very dangerous to children's fingers.

bunabhucan• 3 years ago

Look around the door the next time you open it. You are compressing a rubber gasket that keeps out noise/water etc. out.

mulmen• 3 years ago

They don’t require slamming at all. Just pull them closed. It’s really very easy. Follow through.

sleepytimetea• 3 years ago

I got a new(used) car which has power closing doors - you just bring them close to the car and the motors gently pull them closed. Luxury feature because you never slam or even shut the doors anymore, they are closed soundlessly. I didn't know I wanted the feature till I got this car...now I wish all cars had this. I bet I won't feel the same when I have to pay a thousand dollars to get a single motor replaced.

sh34r3• 3 years ago

Car doors are unlike any other door in your common, daily life contexts. They are not rectangular. They are heavy and float several inches above the ground. They have hydraulics and/or springs, and typically have two fixed points where they will remain open, even in moderately high winds. They have electronics, power windows, crumple zones, and side airbags. They lock remotely. Their latches and handles are very different from other doors.

A car door is like a bedroom door in the same way a MacBook is like a Cray supercomputer. A door is a door and a computer is a computer, but there is significant variance within that category.

poulpy123• 3 years ago

Why would leaving the door open drain the battery is there is no light whent he door is open ?

oaw-bct-ar-bamf• 3 years ago

I can only guess: Probably some vehicle control unit (multimedia/dashboard) thought it had to stay powered on. Door is not fully closed - driver might want to enter the vehicle again any minute and start driving again. better keep the infotainment/vehicle computer in an alive state so the driver experience is not interrupted by a booting system once he re-enters.

bityard5• 3 years ago

One thing I haven't seen mentioned yet: If your battery is dying way sooner than it should be, and if you have _any_ aftermarket equipment installed (radio, backup cam, alarm, remote start, trailer light module), that should always be the VERY first thing to suspect.

These things are not engineered to the same requirements as the OEM electronics, and if they are drawing 10s of milliamps while the car is off, that is certainly enough that you wouldn't notice an issue with a newer batter and a car being driven every day. But if your driving patterns change and the battery gets older, suddenly your battery is dying all the time and "nothing has changed."

sizzle6• 3 years ago

Also 12v USB phone chargers that stay hot when the car is locked. This drove me crazy thinking it was a car issue draining the battery or alternator.

ljf• 3 years ago

This is exactly what happened to my car - I fitted a reversing sensor (this was some time ago).

About a month later the battery was flat - but we didn't drive that often so I thought it might be that. Charged it and was fine for another month or so, but then it started to happen more and more frequently. I took to disconnecting the battery each time I parked up the car.

It was only when I came to scrap the car (for unrelated issues) and went to remove the reverse sensors to use on another car that I saw a single thread of wire that was running off the reverse light, was causing a short. Ah well - lesson learnt!

frankus• 3 years ago

A recent HN post mentioned that a signal like radar from a nearby airport can sometimes be enough to kick the keyless sensor module out of sleep mode and drain the battery. (This was the one about CAN injection attacks).

IshKebab• 3 years ago

Since I don’t have Mazda’s proprieratry M-MDS diagnostic tool, I couldn’t disable the keyless module in software myself.

Ugh, imagine if normal computers were like that. "Since I don't have Intel's proprietary I-DBT diagnostic tool, I couldn't disable the wifi in software myself."

I guess we're half way there with phones.

swamp40• 3 years ago

New Mechanic: Low battery is causing your low battery

Ok, thanks.

irrational• 3 years ago

Sometimes I wanted to pretend the problem didn’t exist more than I wanted to fix it.

Story of my life.

anodyne33• 3 years ago

tl;dr my dealer had my car for a week to diagnose an intermittent electrical gremlin.

My maddening intermittent electrical gremlin was with my new to me Mazda3. Occasionally and randomly after in the first few months I had it the throttle would "go to sleep" during normal driving. By that I mean in the process of normal driving I'd suddenly have no throttle response, the car would go to idle, and the only way to get it back was to completely get off the gas pedal and it would respond again as usual. I'm appreciative that worked, but I couldn't shake the idea that if that were to happen during hard acceleration bad things could happen.

My first trip to the dealer yielded a recording in the event log of the throttle shutting off because it saw throttle and brake at the same time, an expected behavior I was told. I assured the mechanic and service manager that I was almost certain this wasn't the case, they had no other explanation, I continued to have the problem and made certain when it happened that I hadn't somehow been on both pedals.

After an email to Mazda's support line with some technical details hoping to get my situation into the right hands, I got a call from the dealer asking to hang onto it until they could replicate the problem.

The service manager or someone else in the shop drove it for the better part of a week, taking real time telemetry while they were in it while I was in a loaner.

Turned out that the problem was the second brake switch hanging on. I found out that there's one switch that talks too the ECU and another that talks to the brake lights, the former being the culprit.

Frustrating as could be, but like a good nerd I found the final diagnosis fascinating. I also wonder and would like to believe that my detailed and informed email to the mother ship made someone pass it up the line until it got into the right hands.

WillPostForFood• 3 years ago

This is a like a metaphor for modern life with technology parasitically draining time and energy from humanity with shit apps and buggy software while the "mechanics" refuse to even acknowledge there is a problem.

l00sed• 3 years ago

I did a write-up when my car battery died on the way to fish fry. Testing for parasitic draw is no fun. https://l-o-o-s-e-d.net/car-hacking

matt-attack• 3 years ago

Couldn’t he have just measured the resistance of the fuse to determine the current flow? He knew the voltage drop.

Baeocystin3• 3 years ago

Harbor Freight sells a $15 cheapie solar panel (with diode) that plugs straight in to a car's cigarette lighter that essentially 'solves' most parasitic drain problems, if you park outdoors, at least.

https://www.harborfreight.com/15-watt-solar-battery-maintain...

(Not all cars have ports that are live with the key off, but the panel has other ways to wire it)

umvi• 3 years ago

I have a 2013 Mazda 3 and I've had to replace the battery every year for the past 3 years. I wonder if I have this exact same problem? I don't want to disable the wireless key system though because I like being able to lock/unlock the car without pulling the keys out of my pocket. Is there an alternative to this workaround?

NotYourLawyer• 3 years ago

I had a car that would drain its battery if you let it go a week or two without driving it. I just got a trickle charger and left it connected, problem solved.

Not really a great option to leave the hood up all the time if you park outside though.

abosley• 3 years ago

I sold my MazdaSpeed 3 due to a parasitic drain - it was at the dealership for 4 months at one point - with no resolution.

chemmail• 3 years ago

This guy should look into replacing the fuse/relay for that module. Sometimes the relays can get stuck. Thats what happened to my leaf as it would get a TCM error and drain the battery every 3-4 days. Finally figured it out after a year too lol.

xattt2• 3 years ago

Yes, but then where is the story of struggle and sacrifice of having to use a metal key each time to unlock the car?

dmuller2• 3 years ago

Hello, author here. I edited the article a bit for brevity. But, yes I started by checking all the fuses and relays. I didn't find any bad relays. Unplugging the ROOM fuse also fixed the problem, but at the expense of other interior features (like my stereo).

sizzle6• 3 years ago

Why couldn’t he just pull a fuse sending power to one of these systems instead of dismantling the dash to get to the wiring harness?

dmuller2• 3 years ago

Hello, author here. I did do as you described first---I pulled the ROOM fuse and the draw also went away. But, at the expense of more interior features (e.g. my stereo).

sizzle6• 3 years ago

Might have been easier to pull the head unit and tap into a different power relay with that fuse off then dismantle the dashboard, but my hat’s off to you on a job well done!

sizzle6• 3 years ago

I had parasitic draw from a 12v phone adapter that wasn’t powering down when the car was locked, took me forever to realize that cheap Amazon gadget was causing issues!

thehours• 3 years ago

My issue is related to a 12v charger as well, except a little different. Sometimes the car won’t start (engine doesn’t even turn) _until_ I unplug the 12v charger. Then it starts right away. No idea why, but would love an explanation from someone knowledgeable!

sizzle6• 3 years ago

Glad it’s not just me!

anonymousiam• 3 years ago

This can be a problem with any modern car. I had a similar problem with my 2011 BMW, but I was partially responsible. I added a device to the CAN bus between the entertainment system and the rest of the vehicle so my passengers could watch DVDs while we were driving. When the vehicle was off, the ECU would stay awake trying to communicate with the entertainment system, which would fail because the device I added was powered off. The car was brand new and the battery died after a month. I removed (and redesigned) the device so it would provide CAN connectivity when off, but had my battery replaced (under warranty) before I re-installed it.

It sucks that auto manufacturers don't consider the consequences of their design decisions. A malfunctioning (or missing) entertainment system should not cause the ECU to drain your battery.

tempestn3• 3 years ago

Good troubleshooting. More of a workaround than a fix, but quite possibly good enough. I do wonder what it would need to work as designed though. Is there a dedicated ECU for the keyless system that that harness connects to?

honksillet• 3 years ago

I’ve been wondering if my old HOUSE has parasitic electrical currents but I’m not sure where to start.

abbeyj• 3 years ago

There are devices you can get to monitor each one of the circuits from the breaker panel like https://www.amazon.com/Emporia-Monitor-Circuit-Electricity-M... . This would let you narrow it down to a specific circuit. Figuring out what's connected to that circuit and actually taking up the power might be more difficult.

tvarghese73• 3 years ago

I had a 2005 Acura RL which had some pretty fancy electronics for its time. I gave it to my daughter a few years ago and she started reporting that the battery was dying. It would take several days to die, so at first she just jump start the car every couple of days. When she brought it home (she lives 5 hours away) I measured the current draw at >800mA when it should be <20mA.

These cars have a Bluetooth handsfree module that goes bad and starts leaking power. The fix is to bake them in the oven at 350F for 5min to reflow the solder. Already did this twice and then decided to just get rid of it. So that was not the problem.

She needed to get back so we figured out which fuse was the easiest to remove and she lived with that for a couple of months. In the mean time we figured out it was the MICU module, which is the module that controls all the electronic systems and security. Without this nothing works. I was told a new one would be north of $1200 and labor. If they could find one. The dealership said they would chase down the problem again for $165/hr just to be sure... And I would have to leave the car with them until they were ready. Possibly 3 weeks.

I found a couple of the units on ebay for <$100. One was from a 2008 and another one that had some broken plastic on the case for from an early 2005 (same as my car). I tried the first one, nothing worked, all kinds of systems failed. I learned there was an EEPROM chip in the Honda/Acura MICUs that store the codes to make the systems work and are unique for each vehicle. The Dealership can program them for a fee. Having a full electronics lab, I swapped the chips in no time. It was better, but the starter would not engage. In desperation, I did it again on the 2005 MICU and... success!

Mind you, it took >4 hours the first time to get the MICU out and 2 hours to put it back in. I did this at least five times. I got good enough at it that I could do the whole swap in less than an hour. Back and hands were not happy each time I did it for a day or two.

weq2• 3 years ago

Mechanics are pretty big on youtube, i learnt this type of diagnosis from https://www.youtube.com/@JimmyMakingitwork . He posts daily videos of life in the workshop, so the OP would of saved himself some time if he viewed!

Repairing your car is just like programming, mechanics come in many varieties too.

nickpeterson• 3 years ago

My father in law bought a used Jetta that kept having the battery die. Kept going to mechanic and couldn’t find anything wrong, eventually they discovered a hidden gps device that an old dealer must have installed and forgot to remove.

rr808• 3 years ago

I bought an ODB bluetooth adapter. Left it in and kinda forgot about it, kept getting flat batteries. I never expected it to draw so much current.

1letterunixname• 3 years ago

My VW van has a parasitic drain because it's a VW with shitty wiring.

The starter positive wire runs 4 m / 12 ft from the back to behind the passenger seat.

I had to completely redo the dash wiring because the entire thing was a corroded flex "PCB" like the inside of an Apple II or an Atari 2600.

ejcx• 3 years ago

I'm happy you fixed it. I would have nearly lost my mind too. Hopefully figuring out the issue and fixing it is as rewarding as the problem was maddening

jakobsandberg• 3 years ago

You wouldn't need a car if you lived in San Diego - it's the most bike friendly city in the US!

WalterBright• 3 years ago

My experience with car mechanics is they are good with mechanical systems, but have little understanding of anything electrical, and even worse with electronics.

P.S. If you're doing a bit of wiring on the car, don't use those crimp on wire connectors. They'll work ok for a year or so, and then start behaving erratically, slowly getting worse and worse. This is because the crimp is simply not tight enough, and the mating surfaces start to corrode.

The best solution is to strip the wire ends, slip some heatshrink tubing over the wires, cut the plastic off the butt crimpon connector, crimp it on, solder the wires to it, move the shrink tube back over the joint and shrink it on.

This goes for any crimpon connector.

Also, don't use the auto wire you get at your local auto parts store for anything in the engine compartment. It won't last in the heat. You gotta get heat resistant wiring.

xyst• 3 years ago

Personal vehicles are getting way too complicated now. Too many electronic components that can be points of failure.

Recently viewed a video on “steer by wire yoke”

https://m.youtube.com/watch?v=agMrewRJTow

It’s very interesting but there are so many additional motors, sensors, and actuators to simulate the same experience as mechanical based steering.

If you lose electronic assistance in traditional mechanical based steering, you have to apply more force as a driver and makes the experience difficult.

What happens if I lose one or more components in this “steer by wire yoke”? Seems like as a driver you are shit out of luck. If you are a pedestrian, bye bye.

All I want is a walkable city with public and alternative forms of transportation. All of these “car innovations” are mostly useless.

dclowd99013• 3 years ago

Well, they’re also incredibly noisy and unreliable. I’d be willing to bet most of the ecu code is simply Bayesian filters to deal with terrible sensor data. Cars are hard environments to get the kind of high fidelity readings you really need for the nitpicky engines they have now.

dclowd99013• 3 years ago

Electrical issues on cars are the absolute most maddening things to diagnose and fix. I’ve restored several cars and worked on every car I own and the one thing I loathe to do is figure out an electrical failure. Even in older cars, it’s a pain in the ass.

I have an 89 e30 and one time the dash cluster started acting up. Essentially the tach and speedo weren’t responding (they’re not cable driven). Took out the cluster, checked all the connections, checked the wiring diagram to see if there were any potential grounding points I might want to consider. Nothing.

Finally called a local bimmer indie shop and asked them what they thought and they directed me to the small reverse light switch wire that feeds down through the shifter hole into the transmission tunnel. Apparently it often rubs against the body and becomes shorted. I looked and sure enough it was bare. Patched it and all was well.

This wire, mind you, is not at all on the dash cluster circuit. There’s no reverse indicator light on the cluster or anything like that. I would have never had any reason to suspect it was the problem. This is the nature of automobile electrical issues.

sjducb• 3 years ago

I would have fitted a dashboard mounted solar trickle charger and left it at that.

zh3• 3 years ago

A common reason for this (no idea on this specific case) is that the backup battery on the alarm (NiCd) is old/failed. The alarm system then keeps trying to charge it, hence the high (and possibly intermittent) drain.

sgt• 3 years ago

TIL most of HN is struggling with parasitic drains and dying batteries. It's a pandemic!

yellowapple• 3 years ago

Parasitic drains are fun. I usually "fix" them by simply disconnecting the negative battery terminal overnight (or just the specific fuse, if I know which one it is that's causing the drain).

I had to jumpstart a friend's car the other day because she has one of those breathalyzer interlock thingamabobs on it, and between the constant power draw and (probably) a weak battery she had to start her car every day or else it'd be rather quickly bereft of life. Apparently there's a low power mode (hold the button for 5 seconds, then press it again to exit); hopefully that solves the issue.

jackmott42• 3 years ago

We had a Lexus 450h that was doing this, turned out to be the infotainment screen, which includes the backup camera, infotainment, air conditioning control, radio control etc. Replacement part: $24,000

car was worth about $8,000 at that point, so..gone.

aaronrobinson• 3 years ago

I have a drain on my VW Caddy Maxi but had it booked in already for a leisure battery and solar install. When the solar finishes charging the leisure battery the starter battery is then charged. And so hey presto I now have an anti-drain system and haven’t had a problem since. So if you have a parasitic drain and can’t find fix it convert your car into a camper :)

I fixed a parasitic drain on my car in 408 days

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