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Air Conditioner Troubleshooting & Repair

What is Wrong with My Air Conditioner?

It doesn't turn on at all
The fan runs but there's no cold air
The air is cool but doesn't seem cold enough
The unit never turns off
There is water sloshing around inside
The unit try's to start for a few seconds and then quits
A motor is running but there is no air blowing
The unit rattles loudly when it turns off
Water leaks out the front of the unit
The air smells musty
Learn more about air conditioners
Air conditioner parts
Note: If your repair problem isn't listed, click here to email or chat with a repair expert.

It doesn't turn on at all

Check to see if there is power getting to the air conditioner. If it is a 110-volt unit, plug a lamp or other device into the same outlet the air conditioner is plugged into. If there's no power, check the fuses or circuit breakers. If there's still no power, you will need to contact a qualified electrician to restore power to the outlet.

If there is power to the appliance but it is still completely dead there may be a problem in one or more of the following areas:

  • Wiring (Inspect for any broken or burnt wiring)
  • Thermostat
  • Compressor
  • Overload and/or relay
  • Selector switch
  • Control board

Work on these areas of an appliance may require help from an appliance repair person or other qualified technician.

The fan runs but there's no cold air?

Is the air conditioner completely dead? See section 1. Is the thermostat knob turned to the proper setting? Is the compressor motor running? The compressor is a football-sized case with no apparent moving parts. It is located inside the air conditioner at the center. Is it humming or making any kind of continuous noise or causing the lights to dim? If it is making a continuous noise, and your air conditioner is still not cooling at all, there may be a serious problem with one or more of these areas:

  • Compressor
  • Condenser
  • Evaporator

These items are not user serviceable. You will need to contact a qualified appliance repair technician to repair these components.

If the compressor is not running but you do have power to the air conditioner there may be a problem in one or more of these areas:

  • Compressor
  • Overload and/or relay
  • Thermostat (Open thermostat)
  • Burnt wiring
  • Bad selector switch
  • Capacitor

The air is cool but doesn't seem cold enough

If the air doesn't seem cool enough it is necessary to use a thermometer to check the difference in temperature between the air going into the unit and the air being blown into the room. Ideally, the temperature difference should be more than 15 degrees. For example, if the temperature going into the air conditioner is 80 degrees, the temperature coming out of the unit should be at least 65 degrees or less. If the difference is 15 degrees or more there is probably no cause for concern. If the temperature difference is less than 15 degrees you should check the following:

  • Air damper

Check to make sure the air damper is closed. If it's open, it will bring in outside air and reduce the efficiency of the unit.

  • Back cover

During the winter season many people cover their air conditioners to protect the unit from the weather. In the spring or summer they will sometimes forget to remove the cover. If your unit has a cover on the outside portion of the air conditioner remove the cover first.

  • Condensing coils

The condensing coils will always be on the "warm" side of the air conditioner. That is, on the side that faces outside of the room to be cooled. Air is drawn into the back of the air conditioner on the sides through vent slots and is blown directly out through the condenser coils. If the coils get clogged with lint, dust and dirt the cooling system cannot provide the cooling necessary. To clean the coils it will be necessary to remove the entire cover of the air conditioner or pull it out of the wall to gain access to the coils. They can be cleaned by blowing compressed air at them or by using a soft bristle brush to wipe the dirt off. It is important to also clean any dirt or lint build-up in the bottom of the air conditioner so the condense water will be picked up by the condensing fan slinger properly.

The unit never turns off

This is normal on some models when fan is set to run constantly.

If the unit is supposed to turn off and it doesn't, it will be necessary to check several things.

  • First, is the unit cooling properly? See the section entitled "The air is cool but doesn't seem cold enough."
  • Next, is the temperature of the room adequately cool? If the room temperature is cold enough try setting the thermostat to a higher temperature. If the unit then seems to work properly leave the thermostat set to the higher temperature.
  • If the unit is cooling properly when it is turned on and the room is not cool enough the problem is probably that the unit is trying to cool an area that is too large for its capacity. Use the following chart to find the appropriate size air conditioner to use:

AREA TO BE COOLED / CAPACITY (BTU/HR)


100 to 150 square feet = 5,000
150 to 250 square feet = 6,000
250 to 300 square feet = 7,000
300 to 350 square feet = 8,000
350 to 400 square feet = 9,000
400 to 450 square feet = 10,000
450 to 550 square feet = 12,000
550 to 700 square feet = 14,000
700 to 1000 square feet = 18,000

If the room is heavily shaded, reduce needed capacity by 10%

If the room receives a lot of direct sun, increase needed capacity by 10%

Add 600 Btu/Hr for each person in the room if there are more than two people

If the unit is for a kitchen, increase the capacity by 4,000-6,000 Btu/Hr.

If the room size is too big for the air conditioner you have two possible choices. Either decrease the room size by shutting some doors or partitioning off an area of the room. Or, increase the BTU of the air conditioner for that room by installing a different air conditioner with a higher BTU rating.

There is water sloshing around inside

All window air conditioners will remove moisture from the air if there is any. Most window air conditioners collect this moisture in the bottom pan of the air conditioner and attempt to evaporate the moisture. The evaporation process works as follows: First, the water drips down off of the cold evaporator coils on the front of the unit. Then the water collects in the bottom of the air conditioner base, the "pan." If the air conditioner is installed properly it will be tilted slightly back.

The water then collects near the back of the unit. On some units, the fan blade used to cool the rear condensing coils will have a rim on the outside of the fins of the blade. This rim, or "slinger," will come close to touching the inside of the air conditioner pan when the fan is spinning. As the water collects in the pan and reaches the depth necessary for the fan ring to touch it, the ring will lift some of the water up and the fan will blow it at the condensing coils. Because the coils are warm, they will evaporate the moisture to the outside.

While this is happening it is normal to hear water splashing and sloshing around. As long as there is no water leaking inside the room that is being cooled there is no cause for concern.

Never drill into the bottom of and air conditioning unit to "let the water out."

The unit tries to start for a few seconds and then quits

Every air conditioner has a motor called a compressor. The compressor provides the cooling capacity for the air conditioner. If the compressor or its electrical controls are defective the compressor may try to start, fail, and create an electrical overload. If the unit does create an overload, every compressor circuit is also equipped with an overload safety switch. The safety switch is designed to protect the compressor from burning out. The safety switch will cut the power to the compressor for a certain length of time and then reset itself. When it resets it will allow the electricity to flow to the compressor once again. If the compressor then starts, the unit should function normally. If the compressor doesn't start when the overload resets, the overload will again cut the electricity to the compressor. This cycle will continue indefinitely. (Always allow three to five minutes before restarting the compressor.) If this situation is occurring, unplug the air conditioner and get help from a qualified repair technician. This problem is often fatal to the air conditioner because the cost of repair often exceeds the price of a new air conditioner.

A motor is running but there is no air blowing

Every air conditioner is equipped with at least two motors, the compressor and the fan motor. It is possible for the fan motor to be defective and the compressor to be running. If this is the case the unit will appear to be running and may even sound "normal" but no air is blowing out the front or back of the unit. If, after removing the cover of the unit you discover the fan blade is very stiff and difficult to rotate, the fan motor should be replaced. If the fan blade turns freely the circuit powering the fan motor will require electrical troubleshooting. It will be necessary to have a qualified technician locate the cause of the problem, which may be either a problem with the capacitor, the selector switch or the motor itself.

The unit rattles loudly when it turns off

The compressor in all window air conditioners is a powerful motor. When it starts up - and especially when it shuts off - the whole air conditioner can shake, sometimes loudly. Usually there is nothing that can be done to correct this problem. However, it is possible that the compressor mounting pads and brackets are worn out or missing. If that is the case the pads and brackets can sometimes be ordered and replaced.

Be sure that the air conditioner is securely mounted in the window frame if the unit shakes at all. It is possible for the unit to shake free of the frame if not installed properly.

Water leaks out the front of the unit

It is normal for water to collect in the lower base of an air conditioner. See the section entitled: "There is water sloshing around inside." If water leaks out the front it is usually because the unit is tilted forward in the window frame. All air conditioners should be installed so they tilt slightly back to allow for proper removal of the condensation collected.

The air smells musty

Air conditioners remove moisture from the air. The water collects in the base of the unit. Under normal conditions this water will be evaporated out of the unit. However, it is possible for some water to sit stagnant in the base of the air conditioner for extended periods of time. There is no easy way to prevent this problem. The problem will be reduced if you carefully clean the base of the inside of the air conditioner at least once a year. That will keep any dirt, lint or dust from absorbing the water and allowing mold and mildew to grow. Also, replace the filter behind or in the front cover.

find appliance parts quickly.
This easy-to-use search will help you find appliance parts quickly.
Begin by entering your appliance model number.

Where can I find the model number?
The model tag is usually in a visible location, on the front of
the appliance (not on the back). Example: LSQ8243HQ0

Warning! To avoid personal injury or even death, always disconnect your appliance from its power source--that is, unplug it or break the connection at the circuit breaker or fuse box--before you do any troubleshooting or repair work on your appliance. Also, because some components may have sharp edges, use caution while working on your appliance.

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