Battery Drain Issue

[ViN]

My car’s battery has been draining after sitting for a few days. Battery is 2 years old, alternator is also the same. Mechanic checked and can’t seem to find anything that might be causing it
He asked me today if when I start the car, if anything is out of sorts. The only thing that happens is that even if I turn off everything (radio, ac heat blower fan) when I turn the car back on the next day; the blower automatically starts in the highest setting. He thinks this could be the issue draining the battery. Does anyone have any experience with anything like this? It’s a pita to walk around with the jumper all the time. Thanks.

[uberchris]

Whenever I hear about funky blower symptoms in these cars my first thought is final stage resistor. However, you probably aught to get a proper diagnosis before you load and fire the parts cannon. Diagnosing a parasitic drain is time consuming, but not difficult. Perhaps it’s time to try a new mechanic?

[elrichmeister]

You'll need to do parasitic draw test to find out which circuit is draining the battery. I had this issue earlier this year, turned out it was my radio. Google search parasitic draw test for e46 there are tons of videos on how to do this. You will need digital multimeter to test.

[sapote]

The only thing that happens is that even if I turn off everything (radio, ac heat blower fan) when I turn the car back on the next day; the blower automatically starts in the highest setting.

I would pull out F28 and 37 fuses to see if things change.
The night before, measure the batt voltage after parked to ensure it is not parked with a discharged batt to begin with.

[F2468c]

I had a similar issue. After reading all the threads I was convinced it was the blower because I could hear a noise after I turned off the car that sounded like a fan not turning off. I was wrong. It ended up being my aftermarket tail lights being the draw

[ViN]

Thanks everyone. I appreciate all of your thoughts and suggestions. Will report back as it may help someone else in the future.

[kostnice]

its likely the bluetooth module in the trunk, unplug it and see if drain goes away.

[specializedbndt]

I had a similar issue a long time ago with my old m3. As others have said, you need to do an amp draw test. After the car would go to sleep, i had to crawl through the trunk and start pulling fuses to find the circuit that was creating the excess.

[01 Carbonragtop]

I had a similar issue a long time ago with my old m3. As others have said, you need to do an amp draw test. After the car would go to sleep, i had to crawl through the trunk and start pulling fuses to find the circuit that was creating the excess.

Yep this is the way to do, a bit time consuming but well worth it,

[elbert]

After the car would go to sleep, i had to crawl through the trunk and start pulling fuses to find the circuit that was creating the excess.

Could one attach the multimeter leads to the jump-start points under the hood, or is that somehow isolated/filtered from the battery? It would make things a lot more convenient.

[bmwfnatic]

Could one attach the multimeter leads to the jump-start points under the hood, or is that somehow isolated/filtered from the battery? It would make things a lot more convenient.

And measure what? Battery voltage?

The way to do this is to open the hood, trunk, doors and lock the latches using a screwdriver so the car thinks they are closed. Put an amp clamp around the battery cable on the battery itself. Wait for the car to go to sleep and observe the drain on the amp clamp.

Then take your multimeter and measure voltage across each fuse in the fuse box, circuits with a load on it will have a tiny amount of voltage drop across the fuse. When you find the responsible fuse, pull it, and then check back on the amp clamp, if the amps dropped to 0 you found the drain, then figure out which components are on that particular fuse and do further testing (in case of multiple components on a single fuse).

[Nate047]

And measure what? Battery voltage?

The way to do this is to open the hood, trunk, doors and lock the latches using a screwdriver so the car thinks they are closed. Put an amp clamp around the battery cable on the battery itself. Wait for the car to go to sleep and observe the drain on the amp clamp.

Then take your multimeter and measure voltage across each fuse in the fuse box, circuits with a load on it will have a tiny amount of voltage drop across the fuse. When you find the responsible fuse, pull it, and then check back on the amp clamp, if the amps dropped to 0 you found the drain, then figure out which components are on that particular fuse and do further testing (in case of multiple components on a single fuse).

Can you not just attach the meter leads to the battery cable and terminal with plastic clamps, and pull each fuse one by one to see when the draw changes?

[elrichmeister]

When my car a battery drain issue i followed this old you tube video.

https://www.youtube.com/watch?v=KF1gijj03_0

pretty much started pulling fuses to see which one was causing the amp draw.

[elbert]

And measure what? Battery voltage?

Measuring the same thing that you would with the battery in the back. If it wouldn't work, just say so, and that would answer my question.

And why would you need a clamp meter? Why not attach the leads directly to the terminals?

[bmwfnatic]

Measuring the same thing that you would with the battery in the back. If it wouldn't work, just say so, and that would answer my question.

And why would you need a clamp meter? Why not attach the leads directly to the terminals?

To measure Amps you would have to hook up the meter in-line with one of the battery cables. Just easier with clamp so you don’t have to care about anything.