95 5.0L AC problem

My 95 GT AC unit has the following problem; The unit will run perfectly cold for 1 1/2 hours then blow warm air for between 10-20 minutes, and go back to cold air for another 1 1/2 hrs. Engine has UPR pulleys but has had them for over a year and a half, problem is only 6 months old. Is there a fix or do I need a new compressor ? Thanks for any help.

does the compressor stop working?low side cut off switch

does the compressor stop working?low side cut off switch
Not sure, am on vacation but will check and get back to you next Mon.

I am an auto body tech and I'm AC certified in Pa. You're low on freon. When your freon level becomes so low the compressor can only operate intermittently, giving you on and off AC. Once your freon level gets too low, you won't have any AC because the system has a low pressure cut-off switch which will not allow the compressor to kick on if freon is too low...preventing the compressor from burning up.