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Midea R32 M thermal Arctic Mono fault L1

DC bus low voltage protection

Heat pump

What it means

DC bus low voltage protection detected by refrigerant system main PCB. Displayed as P6/H4 on user interface.

Likely causes

  1. Power supply is abnormal
  2. P N +15V wire not connected properly
  3. Voltage between N and +15 is abnormal
  4. DC voltage between P and N is abnormal
  5. Power supply or bridge rectifier failure
  6. Relay on outdoor unit main PCB is open
  7. Inverter module failure
  8. DC bus voltage below minimum threshold
  9. Low DC bus voltage
  10. Power supply issue
  11. Inverter module damaged

Where to start

  1. Check power supply voltage
  2. Check P N +15V wire connections
  3. Measure voltage between N and +15

The full answer, free

  • 47 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 67), 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 R32 M thermal Arctic Mono. Check the model on the data plate before you order parts.

Other Midea R32 M thermal Arctic Mono fault codes