AC not blowing cold

[klwebb]

I picked up a 77 silverado 9 days ago and I'm trying to figure out the ACso I don't fry over the Arizona summer. It comes through the vents fine but doesn't blow cold at all. And ideas or fixes? It's the stock AC system as far as I can tell

[hatzie]

I have a buddy in Mesa that was commenting on hitting 106° temps already... AC is not a luxury item in the Phoenix area.

I'll assume the PO didn't tamper with the system so all the parts are there and connected.

Probably low on or out of Freon. AC systems don't burn Freon so this means it leaked out and you need to fix the leak. Usually one or both of the Schrader valves on the service ports are the culprit.
AC isn't difficult to work on but it's not changing oil or spark plugs either. I wouldn't just give it a shot of freon. Fix it right.

The first good thing is your rig, if it's original, has the big Harrison A6 compressor combined with a massive condenser and pretty big evaporator. It'll cool just fine using R134, even in the desert, if the conversion is done correctly.

Has someone done an R134 conversion? The R134 conversion fittings have an outside profile that looks similar to male Milton Air Tool quick disconnect air hose fittings. R12 fittings are threaded on the outside.

[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.

[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.