Midea M-Thermal Arctic HT R290 Mono fault H9

What it means

Tw2 Zone 2 water flow temperature sensor error. Occurs when Double zone is on (User Interface- For Serviceman - Temp. type setting - Double zone=1), while Main Control PCB cannot detect the right Tw2 sensor value.

Likely causes

1. Flow switch leak due to faulty sealing ring
2. External pump starts before internal pump (PUMPI) starts
3. Flow switch FS plug (CN8) is not connected properly
4. The water flow in the pipe is not consistent with arrow on the flow switch
5. Water flow switch rake mechanically damaged
6. Water flow switch mechanically damaged (rake does not trigger contact closure)
7. Flow switch not installed properly
8. Pump stalling due to impeller obstruction
9. Pump idling due to insufficient water/air in circuit
10. Water pump internal failure despite correct wiring
11. Water pump leak due to faulty sealing ring
12. Water pump connection is correct, the water pump icon on the User Interface is lit, while no indicator lights on water pump is lit
13. Water pump malfunction indicated by abnormal indicator light status

Where to start

1. Inspect flow switch for leaks
2. Check start sequence of internal vs external pumps
3. Verify water flow direction matches arrow on flow switch