E30 Electrical Problem

Hi, I need some help diagnosing a serious electrical problem with our car, a 1990 320iSE. For a couple of weeks, the headlamps and dash lights have been flickering intermittently whilst driving, and last
night the flickering got worse, and the blower motor started slowing and revving repeatedly. The fluctuations aren't particularly related to revs. As i pulled into the car park (about 9 miles later), the engine cut out, and there wasn't enough power in the battery to turn the starter, so it had obviously been draining rather than charging. Had to get a recovery van out, who leant us a power pack to get home on (still flickering). He connected a multimeter across the battery with the engine running and reported that it was charging to some extent, but that the voltage was jumping around all over the place.
First thought was that the alternator/voltage regulator must be dead, but I also fear that bad wiring somewhere could be responsible? Before I start dismantling things and buying expensive parts is there anything else I should test or consider?
Thanks!
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Nedavno MarkS pise:
I had similar problem to yours, and it turned out to be a bad connection from battery negative to body. I just changed that cable, and problem was gone. Check that first.
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Good idea thanks. I'll certainly check that first.
Mark
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That would be my first thought too.
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Thanks John, might well be making a trip to Euro shortly then.
One thing I forgot to mention is that since the problem started some of the dash warning lights, eg parking brake light and those near it, are slightly lit all the time and flickering when driving, whereas they should be off completely. Could a bad alternator cause that kind of behaviour? Thinking about it, I think the lamps that are lit/flickering are those which light when the engine if off, but the key is in position 2, so that could be a clue?
Many thanks
Mark
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Lights which are lit while they should not be lit are usually a sign for a bad ground connection. Try to check all electric wires which have direct contact to the body and should provide a good ground connection.
Frank
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On a 15 year old car alternator brushes/dirty slip rings would be my first guess.
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Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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Make sure you have a good earth from battery to body and also an earth from engine to body. Good luck Clive
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Today I've removed, cleaned and refitted the major earth points in the engine bay, but the problem is still there. I jump started the car, then took it for a drive with a voltmeter across the battery. The voltage was fluctuating between about 11 and 13.8 volts (independantly of engine speed and electrical load) and the dash lights were still doing the flickering thing. The temperature guage also jumps around in sync with the lights. It was worse at the end of the trip (things had warmed up i guess) than the beginning. I had obviously been charging the battery this time, as it had enough in it to start the car when I tried after returning from the drive. Sound like the voltage regulator? I've got a working replacement alternator coming this week so hopefully that will fix it.
Thanks
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Out of curiosity, are you sure the battery is good? Had a loose plate in one once in an older dodge and it would charge sometimes and not the rest. Replaced the alternator with a new one ($225) before finding this out. Pissed me off when I had to spend another $60 on a battery.
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Hi, I'm pretty confident that the battery is good, because it's not that old. I'm fitting a 'new' (used but certified working) alternator this week, so hopfully that will sort it, but if not it didn't cost that much so not the end of the world, will just mean I've got to think again with the diagnosis. Thanks
Mark
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Still sounds like worn brushes to me. Had the exact same thing on a high mileage E34 525. It's a long time ago, but I think the brushes only came with the regulator. Wasn't expensive, though, or difficult to change.
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Thanks Dave, I hope you're right. If this new alternator sorts it out I'll be happy as it's a fairly straight forward job compared to finding a wiring fault or similar. Cheers
Mark
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For the record, the problem did turn out to be a a bad alternator, which I think in turn killed the battery (which only read 10v without load; dead cell). I fitted a replacement alternator and a new battery and these solved all the issues including the strange behaviour seen on the dash lights. It now charges at a stable 14V. At least it was a chance to get all the ground connections cleaned up too so hopefully that will be the end of electrical issues for some years! Thanks to all who contributed! -- Mark
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Thanks for reporting back. Many just go away and we never know if they got the problem resolved.
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