A home AC recharge kit works on air conditioning systems that use R-22 refrigerant. Charging an AC requires refilling the unit with the correct amount of refrigerant to keep the AC running correctly, and prevent ice from forming on the evaporator coil.
To recharge an AC unit, first turn the system on and place the thermostat at the coldest setting. On the outside of the AC unit there are two valves on the pipes feeding into the unit. Remove these by twisting them off or using an adjustable wrench. Using an R-22 manifold gauge, attach the left hose to the valve from the larger pipe. Attach the right hose to the smaller pipe. Open the manifold handles briefly to remove air from the hoses through the middle hose.
Attach the middle hose to the R-22 canister or jug and turn it upright with the valve facing upward. Open the R-22 valve, and allow a few minutes for the pressure to equalize, keeping your eye on the gauge's needles. Once the left gauge's needle stops swinging and the right needle stops shooting upward, check the psi reading on the left gauge. If the psi is under 60, open the left handle for 30 seconds and then stop to allow equalization, but repeat the process until the gauge reads 60 psi. Let the system run for five minutes before placing a thermometer on the large pipe about 6 inches from the valve.
Compare the thermometer's reading to the refrigerant pressure found next to the psi scale on the left gauge. If the reading is greater than 20 degrees above the scale, continue to add R-22 until the temperature reaches the range found on the scale. Once this is achieved, close the R-22 valve, disconnect the hoses and reattach the pipe valve caps.