H11 appears when there is lack of connection between the indoor and outdoor unit or the PCBs are faulty. The system checks all data exchanged between the units during startup. If there is a problem with this data exchange, the error will appear.
The main causes are:
- Bad PCB in the indoor unit.
- Bad PCB in the outdoor unit.
- Improper wiring between the units resulting in improper data exchange.
- Loose connections or damaged wiring between the units.
- Disturbed power supply waveform between the units.