Dan, et al,
I'm not sure about the GM alternator, but I've had this problem with
Lucas alternators more than once. Check, and I mean closely, the solder
connections (3 on Lucas) from the diode pack to the windings. A loose
solder joint will cause 1)high resistance and 2)the bulb to glow.
Charlie
> >
> > Please tell me what to do oh great electrical guru:
> >
> > 1980 1500 mostly stock but with a 1980 GM alternator.
> >
> > My red light is always on dimly (can't be seen in direct sunlight, can be
> > seen
> > in garage) when the motor is running. It has done this ever since I bought
> > it.
> > Changes in RPM has no effect. Putting on the headlights makes it slightly
> > brighter.
> >
> > Voltmeter at battrey shows steady 15v.; about 13.5v - 14v. with headlights
> > on.
> > Battrey is new. Every bulb, instrument, motor, etc... on the car works
> > just
> > fine. I've cleaned every connection I can lay my hands on. Any ideas??
>
> Neil,
>
> My guess is you've got a slightly faulty alternator. It seems to be working
> OK, so I wouldn't worry about it. If you're getting 15 volts at the battery,
> and the battery is staying charged, then there's no problem of any
> seriousness.
>
> When you say you get 13.4 - 14 volts with the headlights on, what rpm is the
> engine turning? If it's over 1500 rpm, your alternator may be a bit weak. A
> weak alternator is usually indicative of a defective regulator circuit or bad
> diodes, which can also be the cause of the light staying on when it shouldn't.
>
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