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Midea M-Thermal Arctic HT R290 Mono fault H1

Communication error between main control PCB and inverter PCB

Heat pump

What it means

Communication failure occurs between the Main Control PCB and the Inverter PCB, triggered after powering on the unit for 2 minutes.

Likely causes

  1. Abnormal power supply to ODU (outside 190-264V range)
  2. Inverter PCB LED2 off indicating inverter fault
  3. Faulty or disconnected communication cable from CN43
  4. Faulty Main Control PCB
  5. Inverter PCB fault (LED2 off or abnormal BUS voltage)
  6. Faulty communication cable between Main Control PCB and Inverter PCB (CN43)

Where to start

  1. Check whether power supply for ODU is abnormal (normal range is 190-264V); if abnormal, adjust power supply
  2. If power supply normal, check whether the LED2 on inverter PCB is off, or the bus voltage between P,N is greater than 280VDC
  3. If LED2 off or bus voltage >280VDC, measure the voltage of the fifth and sixth pin of CN43 on Main Control PCB; if not around 12VDC, replace the Main Control PCB; if it is around 12VDC, replace the inverter control box

The full answer, free

  • 18 more checks in order
  • The readings and component tests from the manual
  • How to put it right, step by step
  • The manual page for this fault (page 105), right under the answer
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Safety: Isolate the outdoor unit and any backup heater, and give the inverter capacitors time to discharge before you open the electrics. Anything on the refrigerant circuit needs F-gas certification.

From the Midea manual for the M-Thermal Arctic HT R290 Mono. Check the model on the data plate before you order parts.

Other Midea M-Thermal Arctic HT R290 Mono fault codes