Room Air Conditioner Repair

Many homes are cooled with room air conditioners. This Fix-It Guide on room air conditioner repair tells how a room air conditioner works, what often goes wrong, how to identify a room air conditioner problem, and what parts and tools you will need to fix it. It then gives instructions for how to maintain the room air conditioner filter and unit case, how to clean the cooling coils, how to straighten the coil fins, how to lubricate the fan motor, and how to check and flush the drain system. You may be referred to service panel repair, fuse repair, electrical cord repair, or motor repair.  If you have central air conditioning, see the Central Air Conditioner Fix-It Guide.

How Does a Room Air Conditioner Work?

Room Air Conditioner Repair

Components of a typical room air conditioner.

A room air conditioner is an encased cooling unit for mounting in a window, through a wall, or as a console. It is designed for delivery of cool air to an enclosed space without ducts.

Here’s how it works: Pressurized refrigerant flows through a room air conditioner, alternately in gas and liquid form. When the unit is on, the condenser pulls in refrigerant gas and pressurizes it, raising its temperature. The heated high-pressure gas travels to the condenser coils outdoors, where the fins distribute heat to the surrounding cooler air. The gas condenses into a liquid that travels indoors to the evaporator coils where, under reduced pressure, it vaporizes into a gas, absorbing heat from the room. The blower pulls room air through the air filter and across the evaporator coils, where it is cooled, then blown back into the room. It makes the room cooler by pulling the heat out of the air. The operation of the unit is controlled by a thermostat.

What Can Go Wrong with a Room Air Conditioner?

With a little maintenance, a room air conditioner should function satisfactorily for many years. The electrical cord may fail. The filter may need to be replaced. The coils may be dirty and the fins bent. The unit may be noisy and it may drip water inside. Routine maintenance includes cleaning or replacing the filter monthly during the cooling season and a yearly lubrication of the fan motor (unless the motor is permanently sealed).

How Can I Identify a Room Air Conditioner Problem?

  • If the unit does not run at all, check the electrical service panel for a blown fuse or tripped circuit breaker. Test the electrical cord . Clean or replace the filter (see below).
  • If the unit repeatedly trips a circuit breaker or blows a fuse, clean the coils and straighten the fins (see below). If the problem continues, the unit may require professional service.
  • If the room air conditioner turns on and off repeatedly, check for and remove any obstruction in the condenser, clean the coils, and if necessary, straighten the cooling fins (see below).
  • If the unit does not cool sufficiently, lower the thermostat and clean or replace the filter.
  • If the unit is noisy when running, tighten the housing screws and make sure clips are in place. Next, lubricate the fan motor bearings (see below).
  • If the room air conditioner drips water inside the room, check and flush the drain system (see below). Some condensation may be normal in high-humidity areas.

Fix-It Tip

During periods of high humidity, water dripping from the drip pan is normal.

What Do I Need for Room Air Conditioner Repair?

Replacement parts are available from the manufacturer and aftermarket suppliers as well as from local hardware stores, electrical suppliers, and home centers. The tools you will need to fix a room air conditioner include these:

  • Screwdrivers
  • Wrenches
  • Shop vacuum
  • Fin comb
  • Light (SAE 10) oil
  • Garden hose

What Are the Steps to Room Air Conditioner Repair?

 Room Air Conditioner Repair

The filter is usually located under the front panel and easy to remove.

Maintain the room air conditioner filter and unit case:

  1. Unplug the unit and remove the front cover.
  2. Remove any clips holding the filter in place and remove the filter. It typically is located either in front of the evaporator coils or is attached to the back of the front panel.
  3. If the filter is not washable, or is damaged, replace it with an identical filter. If the filter is washable, vacuum off the heavy dirt and place the filter in a solution of light detergent and water. Squeeze out dirty water and rinse it with warm water. Squeeze out as much water as possible and let it dry before reinstalling it.
  4. Use a shop vacuum with a brush attachment to loosen dirt from the cover and grilles. Spray the cover with a detergent-water solution and rinse it with clean water.
  5. Wipe the surface clean with a damp cloth.
  6. Reattach the cover.

Clean the room air conditioner cooling coils:

Fix-It Tip

Room air conditioners can be very heavy to move. If you can’t easily remove a window unit for winter, cover it with plastic sheeting and seal it with duct tape to protect it from the cold.

  1. Unplug the air conditioner, and remove it from the window if it is window mounted.
  2. Remove the housing as needed to access the cooling coils. Most units secure the back panel to the chassis with bolts or sheet-metal screws.
  3. Vacuum the coils and evaporator fins with the brush attachment of a shop vacuum.
  4. Make sure all components are clean and dry before reinstalling them.

Straighten the room air conditioner coil fins:

Note: To avoid damage to the coil, use only an air conditioner coil fin comb (available at appliance parts stores) to straighten bent fins.

  1. Unplug the unit from the electrical receptacle. If the unit is wired into the electrical system, turn off the circuit breaker or remove the circuit fuse in the electrical service panel .
  2. Remove any debris with a small brush before continuing.
  3. Match up the fin comb to the fins to make sure that they fit properly and won’t damage the fins.
  4. Carefully fit the comb teeth between the coil fins into an undamaged section above the area to be straightened. Pull the fin comb down, sliding it through the damaged area.

Lubricate the room air conditioner fan motor:

  1. Unplug the unit and remove it from the window or wall.
  2. Remove the unit’s cabinet or cover.
  3. Find the oil ports on the motor housing. If you can’t find any, your motor may be permanently sealed and does not need lubrication.
  4. Remove the caps from the oil ports. Insert a few drops of light (SAE-10) non-detergent oil into each port. Don’t allow oil to contact electrical components.
  5. Insert a drop or two of light (SAE 10) oil along the motor shaft where it meets the motor housing and the fan.
  6. Rotate the fan by hand to work the oil into the motor.
  7. Reassemble and reinstall the unit.
 Room Air Conditioner Repair

If necessary, you can remove, test, and replace the control panel, though this is really a job for a technician.

Check and flush the room air conditioner drain system:

  1. Unplug the unit and remove the front cover. Take the unit out of the window or wall.
  2. If the unit has an evaporator drain pan and a condenser drain pan, locate the drain tube connecting them. Pull out the tube from under the compressor base and run a thin wire through it to loosen any obstruction.
  3. Flush the tube with 1 cup of a solution of chlorine bleach and water to prevent algae formation. If the unit does not have a drain tube, use a cloth to wipe clean the drain channels molded into the drain pan.

Fix-It Tip

Wait five minutes before restarting an air conditioner to lessen strain on the compressor.