i have a 90 f150 with a 300 6. the truck has ac but wont get cold. i have switched it over to 134. the compressor engages but no cold air. i have run the pressure one the little gauge up to 65 psi. nothing. does anyone no what might not be working. thank you

 

Has it worked since you switched it over?
Could be a issue with the slide heat cool controle, may not be moving the door allowing hot air in.

 

no i bought the truck a year ago, and it didnt work. but the truck had been sitting for three years before i bought it. i dont think that it is moving through the system. the little gauge on the ac filler gos up to 45 psi with no change when the compressor is ingaged or not. my gmc will go from 100 with the compressor not ingaged to 45 ingaged. so even though the compressor stays ingaged while on i dont think it is moving through the system. anyone had this problem before.

 

what did you do when you converted it to 134A

 

it didnt work before or after. it like something is cloged and the orfice tube is good

 

You can't just put R134A in an R12 system without doing a number of things first.
To start you must! flush the system out to get rid of all traces of the lubricant used with R12 systems. If the system is clogged and it doesn't seem to be the orifice then it usually is a clogged condenser. AC systems are fairly easy to work on as long as you have the equipment, vacuum pump, and manifold guage set, and the tools to take things apart with.