A/C warm at idle

1995 Corsica, 169,000 miles. Runs great and is in very good condition. A/C blows cold until I am idling. Within a minute, the car overheats, A/C blows warm and humid. I turn off A/C and car levels out. I start driving and everything is ok again. Fluids are checked and ok, Radiator fan works but appears to quit with this problem. Is there a relay that would cause this or a bad sensor that would cause the fan to stop and then cause the A/C to blow warm and the car overheat? Any ideas other than paying "the man" $75 just to tell me something is wrong and pay another $500 to have them try to fix it?
Also, air bag light keeps coming on and off all day, compared to the twice a week it used to flash on and off.

Thanks!

"The Don"