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Daikin Altherma fault U8-01

Connection with LAN adapter lost

Heat pump

What it means

Communication abnormality between unit and LAN adapter. Unit will NOT stop operating.

Likely causes

  1. Faulty LAN adapter PCB
  2. Faulty hydro PCB
  3. Backup heater wiring is NOT correct
  4. User interface is replaced or reset to factory settings; previous measurements are lost
  5. Hydro PCB is replaced or reset to factory settings; previous settings are lost
  6. Backup heater is allowed in emergency mode, setting [4-00]
  7. Faulty room thermistor
  8. Loose or disconnected wires
  9. Damaged connectors or wires
  10. Communication error between bizone PCB and current loop PCB
  11. LD1 not flashing: no operation of LAN adapter
  12. LD2 flashing: TCP/IP communication problem with router
  13. LD3 flashing: communication problem between LAN adapter and indoor unit

Where to start

  1. Perform a check of the LAN adapter PCB
  2. Perform a check of the hydro PCB
  3. Check backup heater wiring, see the installer reference guide

The full answer, free

  • 21 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 61), 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