Mysterious battery drain..

[Bo525i]

My car has started to drain a brand new freshly charged battery out in 2-3 days, to the point of no start, lights, digital clock and the central locking is barely operable :( I have a older fully charged spare to start from and with that there´s no problem untill I install that one, leave it in for 2-3 days, while I recharge the newer one and it gets drained out totally too..

No lights on anywhere when I turn the car off, heater valve not warm!

A short in the trunk harness maybe or something more serious like a defective alternator or generator?

Any advice about how to troubleshoot this?

[pingu]

I think that if there was a short you'd be smelling burnt insulation from an overheated cable. Given that you've got a new battery, sounds like an alternator problem to me. Have you done the OBC #9 test? If not then search this forum/google to find out how to measure the voltage.

[Dr. evil]

have you checked the glove box light?

two ways i know how to find a power drain

1.ampmeter way

connect the amp meter in series with your ground cable and check reading. start pulling fuses until the amp reading drops.

2. voltmeter way

connect volt meter in parallel with the batt and check reading (should be slowly droping). pull fuses until reading stops droping.

Pulling individual fuses should isolate where the drain is in the system.

[Bo525i]

Thx guys

No glovebox light on nor any burnt smell..

I´m no electrical genius so its kinda scary, don´t wanna get fried or short something :D, but I´ll buy a meter and start pulling fuses a.s.a.p. coz its really frustrating with a wimsy electrical system.

Oh and btw. If by OBC test #9 you mean a stomp test thats a no go.. euro model with the small digital clock and temp sensor! And I haven´t found an elegant way of connecting the engine check lamp, don´t want loose wires all over the place.

[pingu]

I've got a Euro car too with no stomp test. The OBC test #9 is something different: you can use the display on which the time is normally shown to measure, and display, the battery voltage. Thus when the car is running, you can measure the alternator voltage.

[Tiger]

Use voltmeter... measure the voltage... red to battery + remote in engine compartment and black to ground... nut on shock tower. When car is off, it should read 12.5V... when car is running you should register from 13.6 to 14.4V... anything lower is bad alternator... which you can try changing the brushes first and then change entire alternator if no help.

[Bo525i]

Ok, measured voltage in engine compartment:

engine off: 12.7
engine on: 14.4

So evidently it isn´t the alternator nor the generator..

Found 1 loose wire (kinda isolated and belongs to the radio harness) behind the radio, measured 7.1 no ignition and 12.6 with ignition.

[Dr. evil]

with the engine off does the voltage drop over time?

[Bo525i]

with the engine off does the voltage drop over time?

Yes it does!

[Bo525i]

Weeeeeee, problem solved :) It was the rear harness after all, I replaced and reconnected all the visible wires and voila.. no more drain :)