Air cond.

I have a 1990 GMC K-1500 5.7 maunel. During the summer when I have the A/C running for about 30 min. on any setting the air coming out of the vents will slow to almost shutting off. It almost sounds like the air is recirculating in the box. It sounds like it's coming from the heater box area. But of course you can't get to anything. Any easy fixes or where this door is located. Thanks for your help.

Sounds like the evaporator is iceing up. Pop the hood when it happens again and see if the accumulator is iced up. If so, you either have too much freon or the pressure cycling switch is bad.

//2000CAYukon