Asked by Jun 15, 2016 at 02:03 PM about the 1975 Chevrolet El Camino

Question type: Maintenance & Repair

My 1975 El Camino has a problem. The generator
light will not go off. The alteranator tests good, the
gages fuse is good,  it shows 12.6 vdc at idle but if
you rev it up, it shows and maintains 14.6 vdc at
the battery while running (until you shut it off and
re-start), however, the generator light will not go
off. The new engine was installed at a professional
shop, the new tranny was installed by a similar
shop, the electrical and tuning wrre both done at
professional shops as well. Someone missed
something but nobody has a clue. Help!

6 Answers


Sounds like the internal voltage regulator has a problem, it should have a low output of 13.8 volts and a high of 14.2, your high voltage is not that far out of specs but the low is too low.

Is it possible tbat voltage is feeding back from the alternator causing the gen light to come on? Charging is not the problem. I tested it a rebuild shop I used to work at. The "A" circuit light is on at rest, the regulator turns on at approx. 600 rpm, charges at around 14.5 no load and around 14.0 with a 75 amp load. On the car, the light should go out when tha alternator is charging. The system shows that it is charging


I know it is charging that is evident from your high voltage reading, it's the low voltage that is off and the fact that it is not turning off the light and the regulator is suppose to do so if it is operating properly. see pic.

Gotcha! Thanks for your parience with me! So, I'm thinking faulty regulator. ......and/or, is it possible for the brown wire to the alternator light to be grounding somewhere, turning on the light, or would that blow the gage fuse?


It would blow and then you would not be able to shut the engine off due to the feedback from the alternator as that lamp is part of the exciter circuit for the alternator.

That makes sense. Thank you. I will replace the regulator. It's the only thing that makes sense.

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