Re-gassing air conditioning car
Determine if you have any refrigerant left in your system at all. To do this, you will need to fit a charging hose on the low pressure port, which is on the refrigerant line on your car, usually near the accumulator. Be sure to use eye protection. If your system is completely discharged, it may be contaminated with moisture, and charging will not give satisfactory results unless the source of the leak is found, repaired, and the receiver dryer is replaced. The open system must be repaired and purged using a vacuum pump to remove air and moisture. You will also want to add compressor oil if the system has been leaking. Evidence of oil leakage and measurement of oil left in a replaced compressor will be a guide as to how much oil to replace.
Check for any obvious leaks. If your system has lost sufficient refrigerant to quit working, you have a leak. Small leaks may take months to deplete the refrigerant so that the AC fails to cool, but charging a system with a significant leak is simply a waste of time. Look for refrigerant oil residue on hose, tubing, and fittings that are part of the refrigerant system. Spray a soapy water solution on fittings and watch for bubbles to appear, indicating a leak.
Make sure the condensing coils are not obstructed with debris, and that the compressor is operating. To test a compressor with a low charge you may need to jump the pressure switch, often located on the accumulator.
Tap your refrigerant can. This is done by completely opening the valve on the tapping fitting, which retracts the tapping pin into the valve body. Failing to do so will result in the tap puncturing the can when it is installed, releasing the refrigerant before the fitting is sealed.
Securely thread the tapping valve on the refrigerant can, close the valve completely shut. This drives the pin into the top of the can, making it possible to release the refrigerant when the valve is opened.
Purge the charging hose. Open the valve until you hear it fill with refrigerant, then slowly loosen the brass fitting that connects the hose to the valve. Be careful not to allow refrigerant to spray on bare skin, as this will freeze skin tissue on contact. Re-tighten the hose once you have heard refrigerant escaping; this should have forced any air (and moisture) from the hose.
Locate the low pressure charging port on the refrigerant line on your car. This will be on the larger tube, usually near or on the accumulator. Connect the quick coupling and make sure it is not leaking.
Crank your engine and turn the AC on high cool, high fan. If your recharging hose is equipped with a pressure gauge, check it to determine if the system needs refrigerant. If the pressure holds steady in the recommended range, the system is full and should not be charged. If the pressure is below the recommended range, follow the instructions to recharge the system.