Unit powers on but compressor never starts; only the fan runs and air is not cold.

Safety: Unplug the unit. Capacitors can store dangerous charge; discharge them properly or have a professional handle testing.

Steps to diagnose compressor not starting:

• Listen for sounds: When cooling is selected, listen for a low humming or clicking from the compressor area. Repeated clicking without start suggests a start component issue.
• Access compressor compartment: Remove the outer shell to expose the compressor, start relay, and capacitor.
• Inspect wiring and components: Check for burnt or loose wires at the compressor terminals and start device. Replace any melted connectors.
• Test capacitor (if equipped): Use a capacitance meter to test the run/start capacitor. Replace if more than 10% below rated µF or if bulged/leaking.
• Replace PTC relay: If the unit uses a PTC start relay, replace the compressor start relay if it rattles when shaken or shows signs of overheating.
• Board relay check: If start components are good, the main PCB may not be sending power to the compressor. A technician can test for voltage at the compressor terminals when cooling is commanded. If no voltage, replace the main control board.
• Compressor failure: If proper voltage is present but the compressor does not start or trips breakers, the compressor is likely failed and requires professional replacement.