Unit powers on but compressor never starts; only the fan runs continuously.

Safety first: Turn off power and discharge capacitors before testing.

• Listen for contactor: When heat is demanded, you should hear a click from the contactor. If not, the contactor coil or control signal may be faulty.
• Check capacitors: Inspect compressor start/run capacitors for bulging or leaks. Test with a capacitance meter and replace if out of spec.
• Measure voltage: With power on and extreme caution, a technician should verify that proper voltage reaches the compressor terminals when called to run.
• Compressor test: If voltage is present but the compressor does not start or trips breakers, compressor windings or internal overload may be open. Compressor replacement is a professional repair.