Battery seems flat until trunk is opened & closed :huh:

Well this has been going on for a few months now. My wife is the Primary Driver of our '02 325i, and frequently she will get in the car and the battery will appear to be completely flat. No lights, no gages, no chimes, no starting sounds, nothing. I replaced the battery about 4 or 5 months ago after the first couple times it happened since the stock battery was nearly 9 years old. I picked up a 49-DL from AutoZone as mentioned in several other threads, namely http://forum.e46fanatics.com/showthread.php?t=268752. The problem still persisted, so I took it down to my local BMW Master Technician and he kept the car for 3 days only to find nothing wrong with it, and of course it behaved for him and didn't die once. She's called me a couple times being stuck at the grocery store saying she needs a jump so I'm forced to leave work and go jump the car, which scares the crap out of me because I don't wanna ruin any of the fancy BMW electronics (I follow the "Approved BMW Procedure").

HOWEVER, just recently I realized that if I open and close the trunk lid, everything gets power again. The lights come on, the chimes sound, and the car starts very strong and easily. Anyone ever heard/seen of similar circumstances?

Any comments/questions/snide remarks will be much appreciated.

I've searched the forum and google for similar circumstances but unable to find anything.

Thanks in advance,
~A.J.

the crimp on the terminals might be loose and when you open/close the trunk, vibration causes the connection to become good again.

Originally Posted by jasonbimmer

the crimp on the terminals might be loose and when you open/close the trunk, vibration causes the connection to become good again.

This.

Also, make sure the positive battery cable is tightened as tight as it can possibly be. Also, take a picture of the cables connecting to the positive battery post and comment back.

Check and retighten the battery cables. Check for any grounds cables loose. Clean the battery terminals if they are corroded. Also check the ground terminal under the bonnet. Not sure how difficult it is to replace the battery cables throughout, you might want to search it. Also, is there any after market stuff in your car? subwoofers? alarms? anything you might think that would cause the electrical short, remove them and test it.

Looks like you have a connection problem in the trunk, but never hurts to check everything at once rather than troubleshoot in steps.

It does sound like it's just a loose connection. Make sure you pull up on the cable, not just tighten it.

But, I think the issue might be attenuated because of your wife's driving habits. If she's not taking it for, say, a 20 minute drive/week, the battery, whether new or not, might not be getting a full charge. If she's stopping at many shops buying stuff...short trips in between...the battery will get weaker and weaker.

Tell her to stop buying stuff and just drive by those shoe stores with "Sale" signs. It'll be hard at first, but in return, she might end up with a car that starts.

Yeah I'm with the guys above me. Sounds like when the trunk is closed it gets a better connection on the terminals.

I had this happen to me last summer. Car would just be dead trying to start. I'd open the trunk, shift some stuff around, close the trunk, and everything would be fine again. For me, it turned out to be a loose connection at the battery. I had a quick disconnect for a trickle charger connected to my battery and I guess that cause the clamps at the terminal to be a little loose. I removed it and tightened everything back up and haven't had the issue since.

Thanks for all the feedback!

Originally Posted by MightyY

I had this happen to me last summer. Car would just be dead trying to start. I'd open the trunk, shift some stuff around, close the trunk, and everything would be fine again. For me, it turned out to be a loose connection at the battery. I had a quick disconnect for a trickle charger connected to my battery and I guess that cause the clamps at the terminal to be a little loose. I removed it and tightened everything back up and haven't had the issue since.

Originally Posted by Shanealan

Yeah I'm with the guys above me. Sounds like when the trunks is closed is get a better connection on the terminals.

I will take a look at it tonight and make sure they're tight as possible.

Originally Posted by dmax

It does sound like it's just a loose connection. Make sure you pull up on the cable, not just tighten it.

But, I think the issue might be attenuated because of your wife's driving habits. If she's not taking it for, say, a 20 minute drive/week, the battery, whether new or not, might not be getting a full charge. If she's stopping at many shops buying stuff...short trips in between...the battery will get weaker and weaker.

Tell her to stop buying stuff and just drive by those shoe stores with "Sale" signs. It'll be hard at first, but in return, she might end up with a car that starts.

I lawled. I think this has had something to do with it on the last battery. The new one seems to be ok, but I don't expect to get 8+ years out of it with her driving habits lol.

Originally Posted by trj

Check and retighten the battery cables. Check for any grounds cables loose. Clean the battery terminals if they are corroded. Also check the ground terminal under the bonnet. Not sure how difficult it is to replace the battery cables throughout, you might want to search it. Also, is there any after market stuff in your car? subwoofers? alarms? anything you might think that would cause the electrical short, remove them and test it.

Looks like you have a connection problem in the trunk, but never hurts to check everything at once rather than troubleshoot in steps.

Originally Posted by insutantu

This.

Also, make sure the positive battery cable is tightened as tight as it can possibly be. Also, take a picture of the cables connecting to the positive battery post and comment back.

The battery terminals aren't corroded yet, since its a new battery but I will make sure they are very tight. No aftermarket electronics on the car. Just the clear corners & tails. I'll take a picture of it tonight when I get off work.

Originally Posted by jasonbimmer

the crimp on the terminals might be loose and when you open/close the trunk, vibration causes the connection to become good again.

This makes sense.


Thanks again to everybody! Really appreciate it.

OP

Any update? Did tightening the terminals fix the problem?

Thx

Sorry for not getting back sooner...

I cranked them pretty good with the wrench in the toolkit in the trunk lid and apparently they were not tight enough. I used a ratchet wrench and really got on 'em, and the issue has disappeared... Now I'm looking for the reason for my faulty Coolant Low light.

make sure it's a faulty light and not cooling system issue.

The level sensor is the same as the windshield reservoir level sensor and you could swap them to see if it's sensor.

Also, a number here have had issues with the ET (if after market)...the magnet on the float seems to drop off and signals low when the coolant really isn't.

But, be careful...it's much safer to assume it's a cooling system issue and not just the level sensor. Make sure you're checking the level in the a.m. when the car is cool on level ground.

Well said dmax.

I've been checking the level a couple of days by looking down into the reservoir. It hasn't been dropping at all. I will try to swap the sensors this weekend and see if it makes a difference. Sorry for being a noob, but what is the ET?

Expansion Tank, and it's beside the radiator and has a cap on it.