Is this common on these older trucks. I hardly ever run my a/c but was waiting on the rain to clear up and went to turn ac and noticed that it wasn't getting cold. As i was heading home i tried it again and while i was moving the ac was cold like it normally is. Do i have a potential problem occuring or is this normal.

 

Could be a couple things, ranging from the A/C charge is low, or the condenser is clogged with shi*t, or the A/C idle up valve is turned off and the A/C compressor wont run at idle.

 

There's a small knob behind the glove box on the ac box it has rpm on it turn it either clockwise or counter clockwise until the ac pump turns on while ur idleing