Alternator voltage erratic (changes with engine rpm increase)

[JOET/CAMRY]

Hello,

My girlfriend has a 1991 Camry 4 cyl. approx. 145,000 miles and it is having an issue with the alternator. When the car is idling the alternator only puts out 12 - 12.2 volts. However, when I hit the gas pedal and increase the engine RPMs the alternator puts out a decent 14 - 14.2 volts.

On my 1989 Camry the alternator voltage pretty much remains the same regardless of engine speed (rpms).

So my question is... is the altenator on it's way out? Not sure if replacing the brushes or the regulator would fix this problem. Your advice is appreciated. Thank You.

JOET/CAMRY

[Doctor J]

Bad brushes are usually indicated by flickering charge light.bad regulator either prevents alternator from charging (like on my car - all idiot ligts were on) or causes overcharge (16.5 volts at 2500 rpm, 90 Cressida).Low voltage on idle (or under load) may also contribute to one bad diode (my friend's 89 Camry) In such case I would take the alternator off and inspect the brushes.If they are good, the diode assembly must be checked for opens;if no problem is found try different regulator. The Autozone store can test the diode pattern