battery drain (repost)

Post Fri Aug 17, 2012 9:17 am

posted this in e36 chat by mistake, so again:

I bought a new battery this year, once after few weeks stationary I had to jumpstart the car, but after that I would not drive it for a week sometimes two and it was fine. 2 weeks ago, and yesterday it did not have power to open central locking .
I've got immobiliser, it's little red pulsing light.
In a passenger door plug rubber is a bit loose, it does not cover the plug completely, but the plug looks dry on inspection.
There is no light in glovebox and never was.
The switch in the boot was loose, I thought that was a problem, after I put that back in position had to check if the light in the boot off when closed (and no you don't have to close your wife in the boot to check it as one zoner suggested in other topic), I put smart phone pointing in the lamp direction in video recording mode and shut the boot, light is off when the boot is shut definitely. Next day battery flat again.
It takes less than 7 hours to drain the battery and it does not die completely, there still dim light when I open boot, even after 2 weeks.

How do I find the problem?
Thank you

Post Sat Aug 18, 2012 11:27 am

willnz wrote:You connect an ammeter in series with the battery. Check what current draw you have

Then remove all the fuses. You should now have almost zero current draw. If not, there is something (alarm etc) connected to the permanent live drawing current so you will need to find what it is.

If current draw is ok with all fuses removed, replace them 1 by 1 and see which fuse is drawing a lot of current.

Then have a look at what is connected to the fuse and check those items for shorts etc.

thank you,

Apparently I was searching for "battery" or "drain" in e36 chat technical help

, when I realised that and searched in e30 tech help I had a good hour of reading.

Post Sun Aug 19, 2012 4:34 pm

left the battery charging for over 24 hours, then put it back in the car and after another 24 hours started fine. hopefully the problem was the switch in the boot and half an hour driving did not give enough charge. gonna check the current draw with ammeter anyway.

Post Mon Aug 20, 2012 7:33 pm

ye, I have to disconnect the battery if I leave mine for a length of time, will have to do the same test with mine soon. I'm not sure but I'm guessing disconnecting the live wire - which is easy on my car - is better than draining and jumping/charging the battery, was told that can wreck it.