Aircon associated problem?

My car made a shreaking sound similar to a belt slipping, then loss of power, rough sound and a bad smell.
I stopped and tested the gears, no proble, not the brakes either, then when i switched the A/C of, the noise and smell stopped. When i swith it on again, it sounds, smell bad and loss of power.
So it seems its got to do wit the A/C in some way. please advise.