first stranding, alternator failure

What you might try if in the mood...

to round out your test with the bulb in-line...

Remove the bulb again and start the car. Test to be sure NO charge from alt. Then rev the engine to 2500-3000 RPM and see if the alt then self-excites...

Sounds like a resistor to give the proper voltage down grade going from the output post of the alt to the excitor wire might be an easy back-up link and still keep the dummy light connected?
 
That's the debate I guess. I know (the hard way) my GM alternator will NOT produce voltage without some sort of voltage going into it. I have not tested beyond knowing 0 voltage = no charge. Resisted voltage (light bulb OR stock idiot bulb working (not lit, just good) = charge. Mine has been cranking out 13.7ish volts like clockwork since I got the bulb happy again.
 
Hey Jeff... How 'bout the next time you have that...

cluster out you PROVE your theory (or ours, Bob, Bernice and myself) with a VOLTMETER... and see if the alternator charges with the indicator bulb removed.

Please rev to 2500 and insure the jumper mod is connected at the alternator.
 
I'm going to add a 35ohm resistor in parallel to the idiot light in my cluster - I don't like having to rev the motor to 2+K when it's stone cold to get the charging circuit energized. I'll need to pull the cluster to replace the coolant gauge anyway.
 
With key on, not running; 1.47v through lit bulb at the alt.'s connection to idiot light. With engine running there is 14.4v there. I ran a straight 12v to it and also had good charge. Disconnected everything, no charge. I'm not going to pull the cluster for this, especially since I'm convinced i had a bad bulb/holder and open circuit when all went south the first time. At least now I know if worse comes to worse I can just jump that wire on the alt. straight to it's own output lug and it will produce, no need for goofy resistors, well, at least as indicated by my short little test (at rpms from idle to 3k). Remember, this is not a Bosch, it's a GM CS130 doing about 100 amps.
 
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