Troubleshooting Tips - Central Air Conditioners

Before you call for service …

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 Causes What to Do

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 cool

1. Thermostat set too high.

1. Lower thermostat setting 5°.

2. Condenser dirty.

2. Clean condenser coil and fins; if necessary, straighten fins.

3. Condenser unit blocked.

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.

1. Clean condenser coil and fins.

2. Condenser unit blocked.

2. Remove debris blocking condenser; cut down weeds, grass, and vines.

3. Evaporator dirty.

3. Clean evaporator.

A dirty evaporator is a common problem
Condenser fan runs, but indoor fan coil blowing warm air (compressor not running) Condenser fan runs, but indoor fan coil blowing warm air (compressor not

Check unit wiring and wiring
connection at the unit, start-switch
and compressor

 Water drips from unit.

 Unit not properly leveled

 Level the fan coil unit.

Condensate drain to condenser pan clogged

Clean condensate drain.

Noisy fan operation

Fan striking

Check for proper positioning and clearance fans.

Loose fan or fan motor

Check for fan tightness on shaft. Check for loose fan

Outside air entering the unit

Check for proper closing of outside air doors

Air across condenser restricted

Check condenser air

Dirty or blocked condenser

Check condenser for blocked dirt. Clean it

Compressor or refrigerant system faulty

Call a professional.

Evaporator ices over




Clogged or dirty air filter

Clean or replace air filter.

Evaporator fan motor tripping on overload

- Check for overheated evaporator fan motor and tripping off on its internal overload / Call a professional.

Unit operating at too low room temperature

If room temperature drops below 70F, the evaporator may ice over.

Unit will not run


Blown fuse / breaker trip

Check fuse / breaker

Broken or loose wiring

Check voltage at switch. If there is proper voltage at switch but no continuity thought it, replace switch / Call a professional.