Fails to Start
Check power source.
Check control switch setting.
Only compressor fails to start.
Drop in power voltage.
Defective compressor capacitor.
Check capacitor.
Replacement.
Check circuit breaker and fuse.
Gas leakage at feeler bulb of thermostat
Check control switch.
Only fan fails to start.
Improper wiring.
Improper thermostat setting 
Defect of fan motor capacitor.
Loose terminal connection.
Irregular motor resistance ( 
).
Irregular motor insulation
( 
). Improper wiring
Replacement of fan motor
Irregular motor resistance (
)
Irregular motor insulation ( 
)
Replacement of compressor (Motor damaged)
Regular but fails to start
Replacement of compressor (locking of rotor, metal)