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How to Repair Central Air Conditioners

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.