Troubleshooting Room Air Conditioners

When it's sweltering outside and your window air conditioner isn't giving you relief, you don't want to wait for a professional to show up. Check the following chart to see if the problem is something you can fix yourself.

ROOM AIR CONDITIONER TROUBLESHOOTING CHART
Problem  Possible cause  Solution 
Unit doesn't run


 
1. No power.


 
1. Check cord, plug, and outlet.
    Check for blown fuse or tripped
    circuit breaker at main entrance
    panel; restore circuit. 
  2. Motor overload
    or safety shutoff. 
2. Wait 30 minutes; press reset
    button. Repeat if necessary. 
  3. Switch faulty.

 
3. Check terminals and insulation; if
    burns are evident, replace switch. If
    switch looks all right, call a professional. 
Fuses blow  1. Circuit overloaded.  1. Put on different circuit. 
  2. Voltage low.
 
2. Call a professional or the
    power company. 
Cooling
inadequate 
1. Thermostat set
    too high. 
1. Lower thermostat setting 5°.
 
  2. Filter dirty.  2. Clean or replace filter. 
  3. Coils dirty.  3. Clean coils. 
  4. Condenser blocked
    from outside. 
4. Make sure outside of unit
    is not blocked. 
  5. Motor faulty.  5. Call a professional. 
  6. Compressor faulty.  6. Call a professional. 
  7. Coolant leak.  7. Call a professional. 
Fan runs, but
unit doesn't cool
1. Thermostat set
    too high. 
1. Lower thermostat setting 5°.
 
  2. Thermostat faulty.
 
2. Test thermostat; if faulty,
    replace, or call a professional. 
  3. Coils dirty.  3. Clean coils. 
  4. Motor faulty.  4. Call a professional. 
  5. Compressor
    faulty.
5. Call a professional. 
Unit cools, but
fan doesn't run 
1. Control switch
    set wrong. 
1. Reset switch; try different settings.
 
  2. Fan clogged.  2. Clean and tighten fan blades. 
  3. Fan blades bent.  3. Straighten fan blades. 
  4. Fan motor faulty.
 
4. Replace fan motor or
    call a professional. 
Unit turns on
and off repeatedly 
1. Coils dirty.
1. Clean coils.

2. Filter dirty.  2. Clean or replace filter. 

As you can see, there are many parts that can fall into disrepair on an air conditioner. You can learn how to fix many of these, such as the filter and coils, 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.