Panasonic Air Conditioner Error F91

DIY Fix Initial user-level checks

1. Power off the air conditioner and wait a few minutes, then restart
2. Check that the filter is clean and not overly blocked
3. Ensure remote control is working and batteries are good
4. Observe and record any blinking indicator lights or error displays

Technician Only Professional diagnostic and repair

1. Use HVAC manifold gauges to check refrigerant pressures and diagnose flow abnormalities
2. Inspect refrigerant piping for leaks (oil residue or frost patterns) and repair or replace as needed
3. Check sensors and electronic control modules tied to refrigerant circuit monitoring
4. Perform system evacuation and recharge with correct refrigerant if leakage has been repaired

Parts needed: Refrigerant piping and fittings, Refrigerant (appropriate type), Sensors and electronic controls, Compressor controls as needed