1. Outdoor unit does not come on
  a. No AC power to unit
- Defective breaker
- Wire burned at disconnect
- Transfer to electrician
  b. Defective contactor
  c. Defective thermostat
  d. Defective transformer
  e. Dog chewed through low voltage wire
  f. Wire burned off contactor


2. Circuit breaker trips when unit comes on
  a. Weak breaker
  b. Grounded compressor
  c. Condenser fan motor shorted to ground
  d. Defective capacitor


3. Outside unit hums but fan does not run
  a. Defective fan motor
  b. Burned wire at contactor
  c. Defective capacitor


4. Outside fan runs but compressor does not
  a. Burned wire at compressor
  b. Compressor out on internal overload
 - Adjust refrigerant charge
- Clean condenser coil
- Defective run capacitor
- Internal compressor failure
  d. Defective start capacitor
  e. Add hard start relay
  f. Defective high pressure switch


5. Heat pump freezes up w/ice
  a. Normal operation during cold weather
  b. Low on refrigerant
  c. Defective defrost timer
  d. Defective blower motor
  e. Dirty filter
  f. Dirty evaporator coil


6. Cool air blowing from vents during winter
  a. Defective reversing valve
  b. Low on refrigerant
  c. Heat pump not running
     - See #1
 
7. Emergency heat does not work
  a. Heat strips burned out
  b. Defective limits
  c. Defective thermostat
  d. No AC power to the air-handler
  e. Wire burned off at the air-handler


8. Outdoor unit runs constantly
  a. Low on refrigerant
  b. Returns pulling attic air
  c. Defective thermostat


9. Indoor fan does not come on, outdoor unit running
  a. Defective blower motor
  b. Defective capacitor
  c. Evaporator extremely dirty
  d. Filter dirty


10. Air temperature fluctuates from room to room
  a. No dampers installed in system
  b. Dampers not adjusted for proper air balance