Sorting out the last few nitty gritty problems before the old girl can hopefully go back on the road!
With the key out of the ignition the battery is going flat overnight.. 1986 320 with 318is engine.
I have tested and noticed the following things so far, with the key out of the ignition:
Alternator is warm when everything else is cold
Alternator is drawing 12v
Ignition is drawing 12v
Are any of these things reasons why it would be going flat?
Many thanks!
Battery draining
Moderator: martauto
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Brianmoooore
- E30 Zone Team Member
- Posts: 49358
- Joined: Mon Jan 10, 2005 11:00 pm
If the alternator is warm in the morning, that is most likely the problem. A diode in the rectifier will have become 'leaky'.
As a check, remove the smaller cables from the battery + terminal and see if it still goes flat. That will leave just the starter solenoid and the alternator connected, and there should be no current drawn at all.
A meter on a current range should read zero, or even a small 12 volt bulb should show no signs of glowing, if connected between the battery terminal an the big leads terminal clamp.
As a check, remove the smaller cables from the battery + terminal and see if it still goes flat. That will leave just the starter solenoid and the alternator connected, and there should be no current drawn at all.
A meter on a current range should read zero, or even a small 12 volt bulb should show no signs of glowing, if connected between the battery terminal an the big leads terminal clamp.
disconnect the earth and put a multi meter between the earth and the earth battery terminal that will show you what the current draw is there shouldn't be any. if there is hold the multi meter there and get some one to pull the fuses one at a time until is stops drawing then that will show what circuit is drawing the power.
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Brianmoooore
- E30 Zone Team Member
- Posts: 49358
- Joined: Mon Jan 10, 2005 11:00 pm
This is the 'standard' plan of attack for a battery drain problem, but since we already have a prime suspect in this case, in the form of the alternator, this 'plan' will only be needed if it tuns out that the alternator is innocent or that there is still a drain after the alternator is replaced.yeti wrote:disconnect the earth and put a multi meter between the earth and the earth battery terminal that will show you what the current draw is there shouldn't be any. if there is hold the multi meter there and get some one to pull the fuses one at a time until is stops drawing then that will show what circuit is drawing the power.
Only fuses 21 to 28 inclusive need to be checked normally, since these are the only ones that are 'live' with the ignition off.