I have been working on the A\C on my 2000 F350. The original problem was that the A/C would blow cold for about 15 minutes upon startup and then start blowing non-cold air. I started by checking for leaks and checking if it was low on freon. There was a tiny leak and slightly low on freon.
I ended up replacing the compressor, accumlator, condensor, evaporator and new oriface tube. We flushed the hoses, and put 9oz of oil and 42 oz of 134a. Hooking up the gauges we get a low side pressure of 60 and high of 225. Everything is sweating and cold. During the hot Houston day the air temp coming out of the vents to 70.
Other Information :
We used a Robinaire 34988 recovery machine and flushed the hoses with a flush gun.
With the truck idling at 2000 rpms the pressure is 26 and 275 and the air coming out about 60 degrees.