charging system gremlin

[strad]

Okay: 91 M42, 80amp Bosch Alternator.

Symptoms are/have been, at times the dash warning lights will stay on after the car is started, yesterday it showed an ABS fault until I stopped the motor and restarted it.  Battery warning light will not illuminate with key in run (motor not running) but it will pulse when car is being cranked.  It is not lit while motor is running.  

Voltage at battery is 11.87 volts with motor off, 11.68 volts with motor running.  So I know the alternator is not functioning.  The question I have is, why is the charge light behaving like that, and does it have any bearing on the alternator problem, or is it caused by a fault somewhere in the alternator.

[tjts1]

It might be time to check your voltage regulator. I'm installing a new one this weekend.
http://www.e30tech.com/forum/showthread.php?t=67639

[roundel318]

I 2nd the voltage regulator, I had something similar driving back 300 miles from Oregon, luckily I had a good optima battery, just lived without AC/Radio, etc, headlights.

My alternator has 266k miles on it.

[strad]

Thanks guys.  A new voltage regulator should arrive on my doorstep in a few hours.  I had a suspicion it might be that as well.  I have not yet removed the old one though to visually check it.  Hope we're right!

edit: well, upon removal of old regulator, it was found that both brushes were worn down to at or below minimums.  They weren't contacting the rotor properly.  New regulator/brush assembly, and we're back to normal charge bulb ops and 13.96 volts at idle.

[///m42 sport]

quick question.  I wonder if my symptoms are similiar?  My check engine light only comes on when the lights are on.  Also is the abs dash light related somehow?  These things just happened today and I'm out of town so have no garage to fix it in