Voltmeter Bouncing

I recently turned my AC (91 Cab) on and realize the this causes the voltmeter needle to bounce between 12 and 14 sporatically, sometimes the engine hesitation is so severe that i feel the car will almost die on me.  The rpm also surges.   I realize this before when the radiator fan comes on, but just not as severe as when the AC kicks in.   Is my alternator going out?

Thanks in advance for any tips.



Billy

Sounds like a compressor issue.
If with no a/c on everything is working then there isn't a base issue.

When you turn on the compressor (don't knw which type you have the Sanden (rotary compressor below alternator) or the York (piston compressor above the alternator), but it puts a heck of a load on the engine when the clutch is engaged and running.  If you are low on gas, then the thing will cycle on and off,,,making your
voltmeter do a dance.

The Fan should come on high speed as soon as the a/c is engaged…

The fan doesn't load the system as the radiator fan is on a relay that is in front of the batter on the inner fender mounted off a bracket that is bolted to a fender bolt.

Cycling Compressors is usually a sign of low Gas.

Check and or replace your main battery to frame and frame to engine grounds, and make sure you have a good ground connection between your compressor and your engine…. I usually use one of the Case bolts on the alternator for the ground for my compressors.

Thank you Briano for your tips, meant to say thanks earlier but problems with my ID and password which prevents me from logging in..

Quick update - as suggested by a friend, cleaned the throttle body and the ICV and it made a night and day difference.  No more hesitation and  surging when AC is on.   However, when parked in idle or neutral, engine RPM still hunts.  I suspect a vacuum leak, will look into that later.