Strange power drain

[Northern]

Alright. My 1990 325is has parasitic drain issues.

With the car off, the head unit for some reason pulls .35A or so via the constant-powered memory wire. I have no idea why it wants so much juice(bad head unit or wiring?), but for now I have a kill switch rigged up to keep it off. This is not my biggest issue though.

With the head unit killed, the car still draws .07a, which some say is a little high. I traced ~.05a or so back to fuse 21, and pulled this fuse.

The car now supposedly has .01-.02a of draw while the car is off. I'd be more than happy with that, except the battery still draws down enough at night that it barely turns over the next morning, and will only click the starter that evening if left alone.

The battery is new last fall, but now it suddenly doesn't seem to hold a charge. I swapped in the battery from my iX, which sits for weeks and starts up no problem, but now this battery dies after sitting for the night, just as the first one did.

It is definitely not the trunk light being on, or antenna, so I'll save people the time mentioning those.

What the hell is going on?

[Northern]

I have traced the draw to Fuse 21, which is "interior lights, radio memory, instrument panel lights, glove box, rechargable flashlight, clock, trunk light, seatbelt gong, ignition key gong"

Although, the entire dash minus OBC,Radio, and tach still works despite the "instrument panel lights"

The big issue is that I've pulled the fuse, and the draw is down to .02A but the battery still dies overnight. Replaced the (new)battery with another known good battery and the same thing happens. It seems like there is a draw, but it could be intermittent, or it only happens after being hooked up for a while. Its possible both batteries went bad at the exact same time, but it sounds too unlikely.



Also, I dropped the newer battery off to get it tested/replaced. I charged it last night, but the test equipment said to charge before testing. They're charging it tonight, and I'll find out the results tomorrow.

[Northern]

the positive terminal of my battery has some sort of alpine amp hooked up to the cable, but I can't detect any draw from it at all, and it has a ground that runs to the chassis end of the negative battery cable.

As far as what is normal, I've heard anywhere from .02a to .06a. I feel my car would tend to be on the higher side of this, so I would be fine with the .07A, considering the OBC is always keeping time.

If a new battery doesn't solve the problem, I'm going to start digging through the functions of fuse 21 and find out what's causing the drain, as well as check into any possibility of the car's charging system killing the battery somehow.

[dnguyen1963]

Here is a useful link...

http://www.popularmechanics.com/cars/how-to/repair/how-to-stop-car-battery-drains

[Northern]

Pretty much what I've been doing so far, but if the battery is not the cause I guess I'm going to have to start getting creative with my testing.

[jlevie]

Normal parasitic draw would be 30-60ma. 0.07a is only 10ma above that and certainly won't drain a good battery overnight. Therefore either the battery is bad and not holding a full charge or there is a greater current draw. You don't say how you are measuring the current draw, but the proper way is to disconnect the ground cable and connect the meter between the ground cable and the battery negative post.

There's no way the head unit should draw .35a while switched off. Either it and the amp aren't correctly installed or there is something wrong with one of those.

[Northern]

Jim: That's the method I've been using.


I got the (newer) battery back, and after failing to read a few times and 20 hours on their charger, it reads within spec. I've thrown it in the car, and tossed fuse 21 back in. The head unit is still off(I'll deal with it later), so the car should only be drawing around 0.07A.

I'm hoping the battery just needed a good charge? Maybe there is something wrong with my charger?

I'll try to start the car again tomorrow morning...

[dogsbark26]

I have traced the draw to Fuse 21, which is "interior lights, radio memory, instrument panel lights, glove box, rechargable flashlight, clock, trunk light, seatbelt gong, ignition key gong"

Although, the entire dash minus OBC,Radio, and tach still works despite the "instrument panel lights"

The big issue is that I've pulled the fuse, and the draw is down to .02A but the battery still dies overnight. Replaced the (new)battery with another known good battery and the same thing happens. It seems like there is a draw, but it could be intermittent, or it only happens after being hooked up for a while. Its possible both batteries went bad at the exact same time, but it sounds too unlikely.

Do you have a rechargeable flashlight in the glove box?

What do you mean "Although, the entire dash minus OBC,Radio, and tach still works despite the "instrument panel lights""? If you are saying the OBC, radio and tach work without fuse 21 in place, that is normal operation. Fuse 21 controls instrument panel lights (not the gauges).

jlevie is (always) correct.

The draw being "down to .02A but the battery still discharging overnight" seems to me to be a clear indication that either the battery is bad or there is more current being drawn than you are measuring.

[Northern]

I have the flashlight connection up under the dash with a small low density foam block over the connection. I do not believe the car came with one.

I am saying that with fuse 21 pulled, the entire center console, cluster, and dash is still illuminated, despite fuse 21 being listed as "instrument panel lights." The only things affected are the OBC, Radio, and Tach/econo gauge.

I just got home, and 24 hours after the battery went in the car turns over with gusto. The head unit was the only thing disconnected the whole time.

I'm starting to think this may have all been caused by my charger.

[the imitator]

I had the same problem with my e34 535i, it was the fusible link in the backseat where my battery is located. In my car its an 80amp fuse that runs off the negative terminal of my battery. I replaced that fuse and I no longer have a problem with my battery barely turning my car over, overnight.

[Northern]

I'll look into that.

The car was fine through friday, and I parked it to fix an exhaust leak at the catback/midpipe connection, but it then rained until sunday, and then I finished and let the RTV cure until tonight(mon)

I went to start the car, and nothing. Interior lights aren't overly dim or anything, but when I turn the key the cluster goes dim and it didn't even turn over.

I guess this isn't an issue of a bad charger, and the battery tested bang on for what it is rated.

I'm going to charge up the battery, then check out what the alternator is putting out to charge the battery... The car runs without the battery hooked up, but it may not be charging even though it has a brand new voltage regulator and was perfectly fine last fall.

Also going to test the theory of a drain that only starts in the rain or after a certain amount of time sitting.

[jlevie]

Running the engine without the battery is dangerous to the voltage regulator and all of the electronics in the car. Don't do that.

[Mr. Schwarz]

Is your trunk closing all the way? I had a drain because my trunk light stayed on since the switch wasn't depressed to shut it off.

[Northern]

Second thing I checked when this started. It turns off when closed, and no amount of jiggling the trunk or car seems to turn it on.

[Mr. Schwarz]

Second thing I checked when this started. It turns off when closed, and no amount of jiggling the trunk or car seems to turn it on.

Thats the only bit of helpful advice I can lend without being there. Sorry man, good luck.