AC not blowing cold

[hatzie]

Originally Posted by Dead Parrot

Based on Hatzie's diagram, get the proper gauge set and check the pressure as is.
If it is empty, you most likely have one or more large leaks. Might even have one or more hoses that have broken down or bad compressor seals. You will need to find and fix before proceeding. Adding freon to a leaky system is a waste of money.
If it is low, you might be able to get by by adding in a can of freon. You will need to verify the type of stuff already in the system. The PO may have tried a non-standard substitute. There is a low pressure cutoff that will keep the compressor from running unless there is enough pressure to turn the switch on. Try to add freon that has a leak finding dye in it. Then check a few days later. It is low for a reason.
If you have a full charge of freon, start chasing electrical issues, blown fuses, loose connections, bad compressor clutch.

I agree on the non standard refrigerant comment. I use R290 in my antiques. OTOH My radiator supports say exactly what's in the system.

For Joe or Jenny Q Public I'd recommend properly flushing, refilling the compressor with the correct amount of Ester oil, vacuuming down, Replacing the dryer, and charging with R134 using the Jungle Eddy method after fixing any leaks or malfunctioning parts.
The mistake most folks make is using the conversion in a box and assuming it will give good performance... you end up with too much oil so performance suffers. R134 with an A6 compressor with TXV or four season expansion tube systems on these trucks should give you 40-45 degree vent temps if done properly.