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Alternator Light stays on......

This is a discussion on Alternator Light stays on...... within the BMW forums, part of the Manufacturers category; I have a '79 R100RS that has started giving me fits. Not long ago the alternator (GEN) light started to ...

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Old 01-23-2009   #1
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Join Date: Jan 2009
Posts: 433
Default Alternator Light stays on......

I have a '79 R100RS that has started giving me fits. Not long ago the alternator (GEN) light started to glow increasingly as the RPM increased. It would not illuminate at idle. I have replaced the alternator and the voltage regulator. Now, the light stays on after the machine has been turned OFF!!! I have disconnected the battery until I can figure out what the heck is going on here. Has anyone experienced anything like this??? HELP. Thanks.
VeloRider is offline   Reply With Quote
Old 01-28-2009   #2
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Join Date: Apr 2007
Posts: 431

Diode board! Be certain to disconnect the battery when you remove the front engine cover (ignition/alternator/diode board) because if just brush the cover on the diode board it will zap just to spite you. It sounds like there is an isolation diode on the board that has shorted, that's what's causing the generator indicator to stay on. The indicator becoming brighter as the engine revs up would also point to at least one rectifier that's blown out.
John is offline   Reply With Quote


alternator, light, stays

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