All,
I have an 83 F150 351W 3Speed. All is well but the air con. I converted it from R12 to R134a a couple of years back and everything was cool (no pun intended) up until recently. The compressor is alive and well and the clutch is doing its thing. It may cycle on and off a bit faster than usual and its NOT cooling down the extended cab truck at all. Call me crazy, but I'm thinking its low on freon. My question is....what should the high and low pressures read on a well serviced air conditioning unit for this truck and how cool should a thermostat(output air vent, not engine) read when the unit is serviced properly?

Any help is appreciated!

Its hot in Texas!

Johnny

 

Generally the low side pressure is about the same as an R12 system, around 20-30. The high side (depends on outside temp when testing) but will run around 175-185 psi (rule of thumb is take temp of day an add it to 100). The engine should be running at 1200 RPM preferably with a fan blowing at the condensor.
The number one mistake is overcharging. R134a does not cool well when it is overchared. The only real way to know for sure, is to recover all 134a and recharge system with correct amount.
If all is well the outlet air temp should be 30-35 degrees.

Mike in Florida

 

Hey Mike,
Thanks for the info. I'll have to keep in mind the fact of overcharging.

Thanks Again
Johnny