Safety: Disconnect power before servicing. The compressor and lines can be very hot.

Steps to address F4:

Improve airflow: Ensure the outdoor side of the Friedrich unit has at least the recommended clearance from walls, furniture, or covers. Remove any obstructions.
Clean condenser coil: Access the outdoor coil and clean it with a soft brush and coil cleaner. Straighten bent fins with a fin comb.
Check condenser fan: Verify that the outdoor fan starts and runs when cooling is commanded. If it does not run or is very slow, test and replace the condenser fan motor as needed.
Allow cool-down: If the compressor overload has tripped, allow 30–60 minutes for it to cool, then try restarting.
Listen for compressor: If the compressor hums and then clicks off, it may be locked or the start components may be failing. A technician can test the run capacitor and overload.
Refrigerant issues: Persistent F4 after airflow and fan checks suggests a refrigerant or compressor problem, which requires a licensed HVAC technician.

Display shows F4, compressor does not start

Possible Causes