Air conditioners ice up when the cooling coil becomes colder than the dew point in the home. A window air conditioner can make a hot day much more bearable indoors. These units are designed to cool no more than one or two rooms, and they work best when the size of the unit fits the size of the room it's cooling. Ice can form on the unit and stop it from cooling if the air conditioner is too large for the room or requires cleaning. Deicing the unit properly to avoid damage takes time, but performing some general cleaning afterward can prevent the problem from happening again. Turn the unit off immediately if the fan is no longer spinning. Continuing to run a frozen air conditioner can damage the unit if the fan has also frozen. Allow the unit to thaw naturally until water begins dripping freely before attempting to turn the fan on again. Turn the air conditioner to the fan-only setting if the fan isn't frozen or after it has begun to thaw. The warm air circulating through the unit can help thaw the frozen coils.

Spread towels beneath the unit inside the home. As the air conditioner thaws, water will drain from the unit. Inspect the unit periodically for thawing. It can take an hour or longer for the unit to thaw depending on the extent of the freezing and whether the fan is able to run. Exchange the towels for dry ones if necessary. Turn off the air conditioner after it has thawed sufficiently for you to access the filter. Remove the front panel of the air conditioner to reveal the filter. Remove the filter from the unit. Clean the filter with warm water and laundry detergent to remove the dust and other debris that could be blocking it. Rinse with clear water. Allow the filter to air-dry completely before replacing it in the unit. Examine the exterior of the unit. Remove any debris blocking the condenser coil vents on the outside of the air conditioner. Debris inside the coils requires complete disassembly and cleaning of the unit, which is best done by trained service professionals. Turn the unit on after it has thawed completely and the vents and filter are clean.

Adjust the thermostat so the unit automatically shuts off when the room is at the desired temperature. Window units are less likely to ice over if they aren't left constantly running. If your air conditioner seems to be losing its cooling ability, the problem may be as simple as frozen or clogged air conditioning coils. Other causes of reduced cooling include restricted air flow and low refrigerant. Even though you may not be experienced in AC service, you can fix all three of these probable causes in several easy steps. Step 1 - Thaw Frozen Condenser Coils Find your electrical breaker box and turn off the switch that controls power to your air conditioner, and allow the coils to thaw. Depending on the ambient air temperature around your condenser unit, it could take up to 24 hours for the coils to melt any ice that is plugging them. Step 2 - Dry the Air Conditioner Coils Once your condenser has had time to thaw completely, remove any pooled or standing water and use a towel to dry any remaining moisture that may remain on the machinery.

Step 3 - Turn the Air Conditioner's Fan On After turning the breaker switch on again to restore electricity to your AC, find the thermostat that controls your unit. Set the thermostat control so that only the air conditioner's blower, or fan, is operating. price for new ac unitThe fan will help melt any ice or frost clogging the coils by circulating air through them.make window ac unit more efficient Step 4 - Heat the Condenser's Coilsbuy window ac units You can speed up the thawing process by using a hand-held hair dryer. Be sure when you use this method of heating that you switch the dryer setting to low heat. A heat setting that is too high can crack the condenser's coils. Step 5 - Check Vent Filters Vent filters, when clogged with dirt and dust, are likely to reduce air flow and conditioner's ability to cool your house.

To maximize cooling efficiency, you will need to check your vent filters. If they are dirty or clogged, replace them with new ones. If you don't have extra filters on hand, you'll find them at most hardware or home improvement stores. Step 6 - Add Coolant Another condition that often reduces cooling efficiency is low coolant in your AC unit. The best way to check for low coolant, and add it when necessary, is to buy a coolant installation kit which you can usually find at a nearby home improvement store. Most of these kits will include directions for adding the coolant. Step 7 - Test the Cooling Capacity Once you have completed the rest of these steps, test your air conditioner's ability to cool. Turn the thermostat setting to "cool," wait a few minutes, and then test the air coming from the vents. If the air blowing through the vent is as cool as you would like it to be, you can rest assured your repairs were successful. How to Clean Air Conditioner CoilsI was a bit surprised to see this question, since this should be readily available information elsewhere, so I did a short search to see if there is a problem finding out the answer. 

It turned out there is, in that there are a lot of incorrect or incomplete answers out there.  The best answer I came across was this:"All air conditioners try to freeze up, that is the goal of the refrigerant... to chill.It is the design of the system that prevents this freezing up from occurring.There are three basic reasons for air conditioner freeze ups:1) The two most common causes of insufficient air flow are dirty filters and under sized ducts. A dirty filter limits air flow which in turn allows the cooling coil’s temperature to drop below freezing. Replacing the filter, monthly, usually alleviates this problem. Under sized ducts will also cause the system to freezeBecause it also limits the amount of air flowing over the cooling coil. This results in lowering the coil temperature and allowing the humidity in the air to collect on the coil and freeze.2)Refrigerant charge. The refrigerant system teeters on a delicate balance. If the system is not charged correctly, the system will not function properly.

This malfunction may result in the poor cooling output and/or freezing up. Only a qualified, certified service technician can properly test and charge a refrigerant system.3) Outdoor temperature. If night time temperatures are too low, the system will not operate properly, and freeze up may occur. The outdoor unit does not function well in temperatures below 60 degrees F. A special “ambient temperature” control must be installed to allow the unit to run properly in cool temperatures, or you may open your windows and save energy."  (, Air Conditioning Freeze Up .)Too many of the answers given on the web assume it is low charge, when it most likely is poor air flow due to an obstruction, which can be the filter, the coil itself being dirty, blocked vents, closed or dampered vents, or incorrectly set fan speed.  It can also be a symptom of too much refrigerant charge.  If the first thing your A/C serviceman does is hook up a bottle of refrigerant to your system, get a new serviceman.