Fujitsu · Waterstage SuperHP Heat Pumps
This error indicates a problem with the inverter system in the outdoor unit, which controls the compressor speed. The outdoor unit may also show '18 Flashes' after pressing the ENTER switch.
Click steps to track your progress.
Turn off the main power supply to the heat pump for 30 seconds, then turn it back on.
Check for any obvious obstructions around the outdoor unit that could cause overheating.
If the error persists, use the 'Reset HP' function (Line 6711) in the control system.
Contact a qualified service technician, as inverter issues require specialized repair.