The compressor is protected by pressure switches or sensors and a discharge-pipe temperature sensor. A low charge, a blocked pipe, dirty coils or a weak fan can all push the pressure or the discharge temperature past the limit, and the unit reports an error.
Where to start
- Clean the filters and both coils; check both fans give full airflow; the outdoor unit must not be covered or breathe its own hot air.
- Check that the service valves at the outdoor unit are fully open.
- Look for leaks: oil marks at flares, brazed joints, valves.
- Measure the working pressure and compare with the exact model's manual under the same conditions; use pipe temperatures to tell a low charge from a blockage (expansion valve, strainer, kinked pipe).
- Charge only after the leak is found and fixed, with the refrigerant type and amount on the unit's label.
Refrigerant work needs the right tools and certification.
Safety: switch off both the indoor and the outdoor unit before opening a cover or touching a board; the capacitors on the outdoor board stay charged for a while after power-off - wait for the board's lamps to go out and measure before touching. Refrigerant and high-voltage work belongs to a certified technician.