[RNajarian]

A while ago I installed a dash mounted volt meter. Recently while driving I noticed some abnormal voltages. I was hoping the brain trust could give me some insight.

The car is a 1975 S with a late 1983 SC motor.

At first everything starts out fine. Engine starts up, generator warning light goes on then off. No noticeable trouble at first. But after a while, what I noticed while driving on the freeway is at a constant speed (2,200 RPM) is the volt meter would drop below 12 volts. Reving the motor didn’t improve the indicated volts. After a while the volts go back to normal by itself, then after some more time it drops back to below 12 volts.

The battery is about 10 years old. Never been drained dead, it looks good, no leaks or bulges.

The next day I ran the engine in the garage with a volt meter for more info.

*Engine off, volt meter indicates battery at 12.13 volts
*Engine running- 2 min after starting volt meter indicates 13.51 v. 800 RPM - no gen light
*Engine running- 10 min after starting volt meter indicates 13.63 v. 1000 RPM-no gen light
*Engine running- 15 min after starting volt meter indicates 13.64 v. 1050 RPM-Gen light dim
*Engine running- 18 min after starting volt meter indicates 12.05 v. 1200 RPM-Gen light brighter. Reving engine makes Gen light less bright but still noticeable.

Shut off engine Gen light goes out completely.

What do you guys think? Voltage regulator and/or alternator?

Thanks