Room air conditioners, also called window units, work the same way central air conditioners do. They are smaller than central systems and often more expensive to operate. Depending on its size, a room unit may cool only the room in which it's located, or it may be able to cool adjoining rooms as well.

Sandwiched between the coils are a compressor, two fans, a motor, and thermostat controls. Dirt is the biggest enemy of window air conditioners; it can lower the efficiency of the evaporator coil, block the operation of the fan that blows out the cool air, clog filters, and block drain ports.

Both of the major components of a room air conditioner are contained in one housing.

Both of the major components of a room air conditioner are contained in one housing.
The condenser coil faces outside, and the evaporator faces inside.

The coils, the compressor, and the motor of a room air conditioner are sealed components, so any repairs to them should be left to a professional service person. However, you can make minor repairs, and regular maintenance will keep your unit running well. When extensive repairs are needed, you can also save the cost of a service call by removing the air conditioner from its mounting and taking it to the repair shop.

During the winter, room air conditioners should be protected from the elements. Either remove the unit from its mounting and store it or cover the outside portion of the unit with a commercial room air conditioner cover or with heavy plastic sheeting, held in place with duct tape.

Caution: Before doing any work on a room air conditioner, make sure it's unplugged. Room air conditioners have either one or two capacitors, located behind the control panel and near the fan. Capacitors store electricity, even when the power to the unit is turned off. Before you do any work on an air conditioner, unplug it and discharge the capacitor or you could receive a severe shock. The unit's owner's manual will show the location of capacitors and tell how to discharge them. Otherwise, let an air conditioning technician do it.

Now that you're ready to work on your air conditioner, try to determine exactly what needs to be done. Look for your problem, and solution, on the chart on the next page.

For more articles on home repair, check out the following links.
  • How To Repair Central Air Conditioners: If your system sends cool air to all parts of the house, you've got central air. Keep the system running cool.
  • Major Appliance Repair: If the a/c isn't the only thing in your house on the fritz, you can learn how to fix other machines in this article.
  • Small Appliance Repair: Once you've tackled the a/c, a toaster or blender seems like child's play. Find out how to fix them here.
  • Thermostat Maintenance: To make sure there's actually a problem with your a/c, you may want to check the thermostat, too. Learn how to calibrate a thermostat.