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soorooshg

3.6 M5 Alternator Trouble

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Yes, the handbrake has a simple switch to ground. That is what makes the circuit to put the light on so is perfectly normal. The other brake light warns of a fault with the braking system such as low brake fluid.

Not suggesting that the BMW garage does not know what they are doing. I'd just be concerned at driving the car for any distance with the voltage so high. 

 

If I had to guess, I'd say there is a problem with the rotor. The exciter voltage does not seem to be getting through it and back to the regulator. Hence the light does not come on. Either way, if it does turn out to be the alternator, charge your battery up before fitting. If the battery is flat, there is a chance the nice new alternator could be damaged. 

 

 

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Guys just an update, thankfully I’ve finally solved the problem!

 

So I did a few more tests with the help of an auto electrician, and he concluded that there was 2 problems, 1. there is a break in the exciter circuit somewhere between the alternator and firewall, and 2. possibly a fault with either the alternator or regulator (which was only installed a few weeks ago). 

 

So we pulled the alternator out again, and for some reason one of the screws holding the regulator had loosened to the point where the back side of it wasn’t making contact with the alternator casing, re-installed it and tightened back up.

 

As for the exciter wire, I cut open the main loom right by the firewall, found the blue cable and stripped a small length of it, and wired in a fresh piece of cable just temporarily to the back of the alternator, creating a new exciter wire. I left the old one there for the time being as I’ll drive it like this for a few weeks just to make sure everything is ok, then go about making it look pretty. Unbelievable how it was such a simple fix but of course with electrics its always the fault finding and investigation which is time consuming. Put everything back together, battery light comes on with ignition, started the car and got a perfect 14.2v on startup, all electrics at full power, very happy. 

 

Thank you so much for all the help and advice everyone has given, I really appreciate it

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Great to see you got it sorted. I've been spectating the thread and in fairness all the help came from just one very knowledgeable @whiskychaser

 

Keliuss

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53 minutes ago, Keliuss said:

Great to see you got it sorted. I've been spectating the thread and in fairness all the help came from just one very knowledgeable @whiskychaser

 

Keliuss

Thanks man and yeah I did post on a couple other forums too so I just copy & pasted this on both threads haha, once again many thanks @whiskychaser

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1 hour ago, soorooshg said:

Thanks man and yeah I did post on a couple other forums too so I just copy & pasted this on both threads haha, once again many thanks @whiskychaser

You are very welcome. Good to hear you got it sorted. Thanks @Keliuss for the kind words too

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