1985 325i auto e30 Battery Drain

[e30-wheels]

I have very bad battery drain, over night the battery will go flat.

Have carried out the following checks

Check voltage drain with meter, 12.2 volt drain with everything turned off and doors unlocked and locked

Remove all fuses at main fuse box 10.3 v drain
Remove all relays as well just in case still 10.3 v drain
Disconnect alternator wires still 10.3 v drain
Disconnect starter motor wires still 10.3 v drain.

All checks have been done 20 mins after ignition has been turned of in case system needs to go into sleep mode.
Before i get deeper into the wiring i thought i would inquire if anyone has had a similar problem or know if anything on the car is wired live to the battery, any help would be greatly appreciated.

I have also swapped the battery for another known good one and the fault remains , everything works on the car as it should with no faults what so ever

Thanks in advance

[KW355]

To check battery drain I put a multimeter in series with the battery positive connection set to current or amps not volts.
If the battery is going flat over night from current drain then you must have a serious drain, probably in the amps range as opposed to milliamps as you would expect.
If the meter shows current drain pull the fuses one by one to narrow the problem down.

[Brianmoooore]

To check battery drain I put a multimeter in series with the battery NEGATIVE connection set to current or amps not volts.
If the battery is going flat over night from current drain then you must have a serious drain, probably in the amps range as opposed to milliamps as you would expect.
If the meter shows current drain pull the fuses one by one to narrow the problem down.

[Yeti]

^^^^ as he said as you can still have 12 volts in a battery but only 20 % capacity working i would get the battery checked.

[e30-wheels]

^^^^ as he said as you can still have 12 volts in a battery but only 20 % capacity working i would get the battery checked.

Battery on the car is 100% good so is the test battery i swapped it for to double check

[e30-wheels]

To check battery drain I put a multimeter in series with the battery positive connection set to current or amps not volts.
If the battery is going flat over night from current drain then you must have a serious drain, probably in the amps range as opposed to milliamps as you would expect.
If the meter shows current drain pull the fuses one by one to narrow the problem down.

I will check the current discharge tomorrow,it used to be about 3 to 4 milliamps all the fuses are out at the moment, i was going to put them back one at a time From fully charged to a dead flat battery is about 5 to 6 hours, taking the alternator , starter and lights out out the equation i dont know what else would draw enough current to flatten a battery in that time.

[KW355]

To check battery drain I put a multimeter in series with the battery NEGATIVE connection set to current or amps not volts.
If the battery is going flat over night from current drain then you must have a serious drain, probably in the amps range as opposed to milliamps as you would expect.
If the meter shows current drain pull the fuses one by one to narrow the problem down.

Whoops ! Thanks for that Brian, If you had 3 to 4 milliamps before it should just be a case of pulling fuses and disconnecting electrical equipment until the drain stops.

[aimlessrock]

have you checked the alternator and the brushes?

[e30-wheels]

have you checked the alternator and the brushes?

As already stated the alternator has been disconnected and the fault is still there, Thanks anyway

[e30-wheels]

Have checked the current discharge and found a 7 to 8 amp discharge with no fuses or relays fitted, Refitted all the fuses, relays, alternator and starter wires and current drain increased to 8.6 amp, pulled fuses one at a time, fuse 21 when removed reduced the drain back to 8 amps, disconnecting the starter and alternator wires again made no difference, switching various things on increased the discharge as it should do, i am now checking to see what is live on the car that is not controlled by a fuse. I have had the car from new and its all standard, apart from the radio which was fitted by the dealer, no alarm or other bits have been fitted.

[BenHar]

Did this just suddenly start or had anything been done to the car beforehand?

Ben

[e30-wheels]

Did this just suddenly start or had anything been done to the car beforehand?

Ben

It started about 6 weeks ago but i have only just got round to sorting it ,have been disconnecting the battery

[e30-wheels]

Did this just suddenly start or had anything been done to the car beforehand?

Ben

It started about 6 weeks ago but i have only just got round to sorting it ,have been disconnecting the battery

The car has had a bare metal respray but that was 3 years ago

[e30-wheels]

Problem sorted i hope, Found two items not fused and wired to a permanent live, one is the Radio and aeriel, the other is the heated door lock This was the problem, the control unit was faulty and staying live, disconnected the control unit, battery discharge now 0.5 to 0.6 mA which are the bits on fuse 21. I can only think the lock heater was wired incorrectly for some reason when the car was repainted as the doors were stripped and removed, The radio must have been wired without a fuse from new. Removing fuse 21 gives a zero mA reading. Thanks to everyone for your help and input.

[KW355]

Just for comparison I think mine had a 10ma discharge when I last checked.

[e30-wheels]

Just for comparison I think mine had a 10ma discharge when I last checked.

When i checked 3 years ago it was 3 to 4 mA now its 5 to 6 thats a draw from the clock and radio memory so it cannot get lower as its zero with the fuse removed there could be a variation in different meters used my present meter is a £15 jobbe.