Troubleshooting Central Air Conditioners

Central air conditions will need some professional maintenance, but there are many minor problems that you can easily fix yourself. If your central a/c unit isn't working properly, look for the problem you're experiencing on this chart and see if it's a do-it-yourself job.
CENTRAL AIR CONDITIONER TROUBLESHOOTING CHART
Problem  Possible cause  Solution 
Condenser
doesn't run

 
1. No power.


 		 1. Check for blown fuses or tripped
    circuit breakers at main entrance
    panel or at separate entrance
    panel; restore circuit. 
  2. Thermostat set
    too high.
 2. Lower thermostat setting 5°.

  3. Motor faulty.  3. Call a professional. 
  4. Compressor
    faulty. 		 4. Call a professional.
 
Uneven cooling

 		 1. Distribution
    system out of
    balance. 		 1. Balance system.

 
Inadequate
cooling
1. Thermostat set
    too high. 		 1. Lower thermostat setting 5°.

  2. Evaporator dirty.  2. Clean evaporator 
  3. Unit too small.
 		 3. Replace with larger unit;
    call a professional. 
Unit doesn't
 1. Thermostat set
 1. Lower thermostat setting 5°.
cool
    too high.  
  2. Condenser dirty.  2. Clean condenser coil and fins; 
        if necessary, straighten fins.
  3. Condenser unit  3. Remove debris blocking condenser;
      blocked.
    cut down weeds, grass, and vines.
  4. Evaporator dirty.  4. Clean evaporator.
  5. Compressor faulty.  5. Call a professional. 
  6. Not enough
    refrigerant in system.		 6. Call a professional.
 
Condenser unit
turns on and
off repeatedly 		 1. Condenser dirty.
2. Condenser unit
    blocked. 
1. Clean condenser coil and fins.
2. Remove debris blocking condenser;
    cut down weeds, grass, and vines. 
  3. Evaporator dirty. 3. Clean evaporator.

A dirty evaporator is a common problem. On the next page you'll learn how to access the evaporator and clean it properly.

For more articles on home repair, check out the following links.
  • How To Repair Room Air Conditioners: Cooling units that you mount in your window have the same job as central air conditioners, but the repair principles are different. Follow these instructions to get your unit running smoothly.
  • 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.