E36 M3 battery drain?| Grassroots Motorsports forum |

rmarkc Reader
4/13/12 5:54 a.m.

During my recent repair frenzy on my E36 M3, a new problem has cropped up.
Part of the repairs I performed was replacing fuel injectors and fixing the driver's window armature. While doing these fixes, I ran the battery down and had to hook a charger up to it to crank the car.

Now the radio doesn't work. It stays lit but won't power on even without the key in the ignition and drains the battery.
The car runs and drives fine when I charge the battery. The alternator charges the battery and I don't have any problem restarting the car once it is run long enough to charge but drains overnight.

The radio is a JVC aftermarket unit installed by the PO. I'm planning on removing the radio to see if it is the cause of the drain but I wanted to get some input from your collective wisdom.

Any ideas?

Flogger00 New Reader
4/15/12 5:18 p.m.

In reply to rmarkc:

Check your current draw one circuit at a time. Radio's a good guess if I understand your description because it's staying lit and since PO changed HU. Maybe amp's not turning off due to HU miswire? Look especially closely at circuits you did touch recently, and also alarm circuit, as IME it's easy with an E36 FOB to trigger things in ways you didn't mean too (BTDT).

HTH

mad_machine GRM+ Memberand MegaDork
4/15/12 5:23 p.m.

check your trunk wires.. E36s are known for the wires going into the trunk getting brittle and breaking. I had a current drain until I found the light switch on the hatch on my Ti was grounding out (the interior lights don't work in my car)