How to Add Refrigerant to a Window Unit

Spread a clean towel or sheet on the floor directly beneath the air conditioner. Unplug the unit, slide it out of the window and set it on the sheet below. Read the identification tag on the unit's inner back cover to determine which type of refrigerant should be used.

Unscrew and remove the screws that secure the unit’s casing, using a screwdriver. Collect the screws in a small container and set aside for use when reassembling the air conditioner. Grasp the casing with your hands and slowly slide it off the unit to reveal a metal cylinder, or compressor.

Inspect the cylinder for the two hose locations. Set the refrigerant can next to the unit. It will have two valves -- one large and one small.

Join the large valve, or the service valve, from the refrigerant can to the larger hose. Then join the smaller valve, or the tap valve, to the smaller hose.

Plug the air conditioner back into the outlet and turn it on. Set it at the lowest temperature setting to begin installation. The refrigerant will flow from the valves to the hoses on the cylinder. Watch the gauge during the recharging process to determine when the pressure reaches 70 pounds per square inch.

Turn off the air conditioner and disconnect the hoses from the valves.

Reassemble the air conditioner's casing, using the screws that you set aside. Make sure the screws are tight enough to firmly hold the unit and casing. Place the air conditioner back in the window.