Engine runs bad when A/C is on

With A/C on and constant throttle, the engine rpm fluctuates in intervals of about one second. The power variation is quite noticeable and visible in the tachometer ( ~200rpm). MIL does not come on.

With A/C off, the engine runs just fine.

Could that be the A/C compressor engaging and disengaging? If so, is it supposed to switch that fast?

I also noticed the voltage drops a little with A/C on, but it is still at about 14V (according to the gauge). The car is a 94 Park Avenue, L27 engine.

Any ideas?

Maybe the belt slips?

Yes, the most likely answer is that the ac compressor is turning on and off. It might be doing this because either the charge is low and when the compressor turns on, the low side is going too low or maybe there is a restriction and the high is going to high. Or maybe the system is working correctly (correctly charged) because the ac does cycle like that under certain circumstances.

Open the darn hood and see if the compressor is cycling, thats the best way to tell.