Adding refrigerant to my car

When I moved to Miami for a year to go back to school full time, I left my XFR at my house in St. Louis. Upon returning, the A/C that had previously worked fine in the car now only blows hot air. I got out my A/C gauges and confirmed that the car is virtually empty of refrigerant. I’d like to add some refrigerant to either fix the air in the car, or at the very least be able to determine where the leak is at.

I disconnected the A/C pressure switch and jumped it to kick the A/C clutch on so I could add the refrigerant, but its not engaging. As much as it pains me to admit it, A/C systems are probably the area of cars I know the least about and my knowledge is pretty basic. I know this is a long shot, but any ideas why I can’t jump the A/C clutch to get some refrigerant added?

I won’t give you the whole spiel as to how to do it right (briefly, pump vacuum; check for leaks). But note that if you have zero pressure (or better still, a vacuum) you can pressurize the system through the high side port up to the pressure in the can. Putting the can in hot water raises the pressure btw. At that pressure, you should be able to engage the compressor and finish charging through the low side port. IMHO.

In this case should one use gas or liquid? (can up or down facing)

Just dump a bit of liquid into the high side enough to raise the pressure to do a leak test. Fix the leak first then evacuate the system down to 500 microns and ensure it holds. Then weigh the correct amount in via the high side breaking the vacuum.

Just be sure that all the refrigerant is not stuck in the condenser before a possible blocked drier or faulty valve, don’t assume just because it is low pressure on the low side that it is low pressure everywhere.


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Thank you all for the replies. I’ll see if vacuuming the system will either show me where the leak is (if there is a larger leak) or allow me to add some freon.