Recharging your Trane air conditioning unit is a task best left to a qualified HVAC technician. However, there may be any number of reasons that you can't hire an HVAC technician; for example, if you live in an area where service is not readily available. You can recharge your Trane air conditioning unit yourself with the proper gauge manifold and refrigerant. Because the refrigerant is under pressure, it is potentially dangerous if you attempt to use the wrong tools.
Check the Trane owner's manual for the correct type of refrigerant and operating pressure for your model. Do not attempt to put R-22 refrigerant into a R-134a system, and vice versa.
Shut off the unit's compressor.
Attach the yellow hose of the charging manifold to the canister of refrigerant. Bleed the air from the lines by opening the regulators slightly on the refrigerant canister as well as the other two lines of the manifold.
Attach the red hose to the heat pump's liquid line service valve or the blue hose to the suction valve. Be sure that all of the regulators are shut off before attaching the hose to the unit.
Open the regulator of the hose you connected, then open the regulator on the refrigerant canister. Turn on the heat pump and note the pressure reading on the gauge corresponding to the hose you connected.
Close the refrigerant canister's regulator once the pressure reaches the appropriate level for your model. Close the hose regulators and disconnect them from the unit and the refrigerant canister.