Truck Repair: air-conditioning, 134a, freon

Question
my air conditioner is intermittant.it comes on in the morning or late evening when the outside air is cool,but not after the truck has sat in the sun during the day.i drive a 1996 chevy 1/2 ton.

Answer
I would say it may be just a little low on freon. You can get a kit for 134A at most parts houses, and add it yourself.
If it fixes the problem right away, you know that was it. Don't add more than one can without getting it checked by someone with experience.
Van