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.

Problem  Possible cause  Solution 
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
4. Call a professional.
Uneven cooling

1. Distribution
    system out of
1. Balance system.

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°.
    too high.  
  2. Condenser dirty.  2. Clean condenser coil and fins; 
        if necessary, straighten fins.
  3. Condenser unit  3. Remove debris blocking condenser;
    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

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.