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Daikin Altherma fault 8H-03

Safety thermostat circuit open with jumper removed

Heat pump

What it means

Stop error 8H-03 occurs if the factory-mounted jumper on X5M terminals 13/14 is removed (open circuit) but a safety thermostat (Q4L) is not connected in its place. The system detects an open circuit on the safety thermostat input.

Likely causes

  1. Jumper removed without connecting a safety thermostat
  2. Open circuit on safety thermostat wiring at X5M terminals 13-14

Where to start

  1. Check whether jumper is present on X5M terminals 13/14 if no safety thermostat is installed
  2. Verify safety thermostat (Q4L) wiring continuity if installed
  3. Remove factory-mounted jumper wire from the respective terminals

The full answer, free

  • 2 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 28), 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 Daikin manual for the Altherma. Check the model on the data plate before you order parts.

Other Daikin Altherma fault codes