How to Add Freon to a Window Air Conditioner

Window air conditioners need a proper refrigerant charge to work properly.

Window air conditioners only cool air efficiently when the unit has the proper refrigerant charge. Refrigerant does not evaporate or wear out. Only leaky systems need Freon added. Freon, a DuPont trademarked name for certain types of refrigerant, has become the generic term used in place of refrigerant. Window air conditioning units, classified as self-contained systems, have the compressor, fan and both the evaporator and condensing coils in a single structure. Window air conditioning units use a single double-shaft fan to blow air over both coils.

Things You'll Need

• 1/4-inch nut driver
• Saddle valve
• Adjustable wrench
• Refrigerant-charging hose and gauge kit
• Thermometer

Instructions

1. Remove the air conditioner from the window. Set it on a secure level surface that can get wet and has an electrical outlet nearby. Look at the identification tag to verify the refrigerant type used.

2. Locate and remove the screws that hold the air conditioner's shell in place with a 1/4-inch nut driver. Lift the shell off of the unit. If the shell does not easily slide off, check for hidden screws in the center of the shell along the top.

3. Find the refrigerant access valve on the thick copper line that comes from the compressor. The access valve comes in two types. A stem valve has a skinny neck soldered into the thick copper line. A saddle valve comes in two halves, in a block shape, wrapped around the thick copper line. In the case of a system without an access valve, install a saddle valve using the valve's installation instructions.

4. Remove the access valve cover with an adjustable wrench. If the stem valve cover's O-ring sticks to the stem valve, remove it and set it back in the cap.

5. Connect the gauge side of a refrigerant-charging hose and gauge kit to a jug of refrigerant. This refrigerant must match the type listed on the tag.

6. Connect the hose side of the charging hose and gauge kit to the access valve. This will charge the hose.

7. Check the temperature with a thermometer. Compare the temperature against the temperature-pressure chart in the air conditioning unit's shell. Find the ideal refrigerant pressure that corresponds with the temperature.

8. Plug the air conditioner into an electrical outlet. Turn the thermostat to its coldest setting. Let the system run for three minutes.

9. Check the refrigerant pressure reading on the gauge. If the pressure reads less than 4 lbs. per square inch gauge (psig) below the ideal pressure,open the jug of refrigerant for 30 seconds. Let the unit run until the pressure reading on the gauge stops dropping and take a new reading. Add more refrigerant as needed.

10. Turn off and unplug the unit. Close the refrigerant jug. Disconnect the hose from the access valve and then the jug. Install access valve caps. Install the shell and set the unit back in the window.

References

• Central Air Conditioner and Refrigeration: How Does a Central Air Conditioner or Central AC Units Works
• Air Conditioning and Refrigeration Guide: Charging Air Conditioning Systems
• Air conditioner Selection: How to Recharge Air Conditioner
• Louisiana Department of Natural Resources: From Freon to Suva

Resources

• High Performance HVAC: Air Conditioning
• Georgia Institute of Technology: Design Analysis of the Einstein Refrigeration Cycle