Going down hwy my truck's a/c will get super cold. Temp sets between Hot & Cold but when I'm in town have little or no a/c. I realize the air going over condenser makes big difference. Does it need can added? Purchased this truck new & system has never been touched. The reason I haven't checked pressures I never have purchased R-134A gauges.

check between the radiator and condensor for a lot of crap built up - on a truck this age it is very possible and I've had good luck blowing the junk out and having the system work again

Area between the radiator & condensor is clean.