I’m not very knowledgeable about this. I have a 1988 Custom Cruiser with a Harrison 622 AC compressor that was converted to R134. It has leaked I’m guessing all of it’s refrigerant, and when I hook my can of 134 up to the port the clutch just keeps cycling on and off. I’ve let it run like that for 20 minutes but nothing changes. The gauge on the can goes up and down as the clutch keeps cycling, but it isn’t blowing any cooler. Any help would be appreciated

 

The clutch is rapid cycling because you still don't have enough freon in the system. The gauge is connected to the low pressure side. The pressure sensor that controls the clutch closes for a while to engage the compressor, but eventually that freon gets pumped into the high side and the pressure in the system drops again, causing the switch to open. I usually have to do this for a while. If the system is really low, it will take 3-4 cans, depending on how much you empty them (it can get really slow at the end). Some people jumper across the harness connector that goes to the switch to keep the compressor on all the time. I'm hesitant to do this. The switch is there for a reason.

 

You can put the cans in the sun for awhile. Or put then in a pan of warm water. For say 30 minutes to an hour. This will raise the pressure in the cans slightly and may speed things up. A/c machines have a heating belt around the refrigerant tank the heat the tank for this very reason.

 

The problem isn't the initial temperature of the can, it's the fact that the temperature drops as you empty it. PV=nRT, so as P goes down, so does T. I actually put the can down near the exhaust manifold to warm it while filling.

 

Thank you!

 

You didn't say where you were starting. If the refrigerant leaked out to the point it equalized with atmospheric pressure, you have air in the system. No matter what you do, that air is going to hinder heat transfer. If you evacuated the system first, then you should be able to flow enough refrigerant into the system to get it to stop cycling.

The thing is, you should do a leakdown test on the system first and find/eliminate any leaks so as not to waste refrigerant. If it's still leaking and if it's a significant leak, you'll be doing this often.

 

Did you pull a vacuum on the system before starting to add freon? You should pump it down to 28 to 30 inches of vacuum and hold it for at least an hour to see if there are any leaks. Also R134 isn't compatible with the mineral oil in a R12 system, you should remove all of the mineral oil and replacement it with PAG.