Tools to add coolant to a car's air conditioning include a recharge kit, gloves, safety glasses and several cans of R-134a refrigerant. Vehicles built before 1995 use R-12 refrigerant that is only available to certified mechanics. The correct recharge kit has quick-connect fittings instead of screw type fittings.
When a car's air conditioning system is low on refrigerant, it does not provide proper cooling. Adding more coolant to the system takes as little as 10 minutes.
The air conditioning system has two ports, identifiable by size. The kit attaches to the low-pressure side of the air conditioning system, which is the smaller of the two ports. The location of the port is between the compressor and firewall of the vehicle.
The charging hose attaches by pulling back the outside collar and pressing the hose fitting over the low-pressure fitting. Once it is in place, releasing the collar locks it in place and a gentle tug should not remove it from the fitting. To read the pressure of the system, the car must be running and the air conditioning set to maximum cool with the fan on high. If the reading is not in the green zone, the system requires more refrigerant.
Adding refrigerant requires attaching a can to the hose and opening the can. The charging process should stop periodically to check the pressure and avoid overfilling.