Window air conditioning units are used by many to cool apartments, homes, RVs and offices. These units use freon to create cool air. The freon is sent through a sealed tube, and should not run out. However, units get old and can develop leaks. When this happens, the unit will need to be recharged by adding freon.
Check to see if the air blowing out of the unit is cold enough. If it feels as if it isn't cooling the way it used to, hold a thermometer up to the unit as it is running. Wait a few minutes for the thermometer to adjust. Look at the temperature and write it down. Also check the temperature of the air being pulled into the unit. Hold the thermometer to the front intake for a few minutes. Write this temperature down as well.
Calculate the difference between the two numbers. If the difference is higher than 20 degrees, then the air conditioner probably just needs to be cleaned. If it is lower than 15, then it most likely needs freon.
Take the unit out of the window so that you can repair it. Undo the panel on the unit with a screwdriver and locate the two lines going to compressor.
Select the larger of the two lines. This is the the tube to which you will need to add the freon. Attach a tap valve to the line by following the directions that came with the valve.
Check the gauges to make sure they are off, and then attach the blue tube to the valve you just attached as well as to the compound gauge.
Turn on the air conditioner to "High" for a few minutes, and then connect the yellow tube to the freon bottle. Open the freon valve. Loosen the yellow tubing at the gauge for just a second and then tighten it back up. This will release air from the tube.
Open the valves on the gauge to start the flow of freon. Watch the gauges and charge the unit until it reaches 70 psi. Turn off the gauges and freon, and then remove the tubes. When you remove the blue tube from the compressor tube where you inserted the valve, remember to close the new valve.