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Daikin Altherma fault JA-17

Refrigerant pressure sensor abnormality

Heat pump

What it means

Refrigerant pressure sensor input is out of range, causing the unit to stop operating.

Likely causes

  1. Faulty refrigerant pressure sensor
  2. Faulty hydro PCB
  3. Poor water flow through high pressure side plate heat exchanger
  4. Incorrect refrigerant charge
  5. Deviation of refrigerant pressure sensor (higher value measured than actual).

Where to start

  1. Perform a check of the refrigerant pressure sensor
  2. Perform a check of the hydro PCB
  3. Check high pressure side plate type heat exchanger for good water flow and heat exchange

The full answer, free

  • 1 more check 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 52), 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.

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