I have an issue on my 1993 Grand Prix:

During the day (no headlights on) it does fine - very little, if any
fluctuation in the volts gauge.

However with the headlights on it becomes noticeable, and the blinker
makes it worse - the gauge actually fluctuates in sync with the
blinker if I'm idling at a stop light. When the engine is under load
(ie passing on a Highway) with headlights and blinker on, the
fluctuations aren't noticeable.

However, if the car is in Park with the lights on, the fluctuations
become minimal, even if I turn the blinker on it still doesn't get as
wild as it does when the car is in Drive.

Does it sound like a bad pulley, or just a bum alternator, or an issue
with the gauge itself?

Thanks,
Kevin

Without the car running,take a voltage reading across the battery with a voltmeter and it should read around 13 volts. Then crank the car and read the voltage again and it should read approx. 14.5 volts. If it doesn't then your alternator is probably bad. Most likely that is the problem.

If the problem only exists when the car is idleing under load, I wouldn't be worried. Engine RPM is only around 600 in gear at idle, and the alternator is turning too slowly to keep up with the extra load. If the fluctuations go away as soon as RPM increases, there's nothing wrong.

the alternater is running too slow to provide power to keep all the electric running...this doesnt mean the alternater is bad. It is normal.... This may indicate your battery is a little weak. There is no need to rush out and get a new battery, unless you live in a really cold climate.....

Probably nothing to be concerned about...as mentioned above...one question though...Is there an audio system in the car with an outboard amp? More specifically....an amp and sub or other speakers?

Thanks to all for all the help.

I had the alternator and battery tested at Pep Boys this AM, and they say everything is behaving as it should. There aren't any aftermarket stero components installed in the car - everything is stock.

I noticed when I have the defroster on (and with the accompanying bump in RPMs), the problem goes away. And while I'm driving the volts hold steady with no fluctuation. The only time it really fluctuates is in idle, in drive, with the headlights on. The fluctuations stop once I accelerate and the gauge stays steady.

Glad to hear its nothing that I should be overly worried about.

Thanks again!

Kevin