Hitachi Yutaki M & Yutaki S fault 17

Auxiliary sensor 2 thermistor abnormally (THMaux2)

Heat pump

What it means

Auxiliary sensor 2 thermistor (THMaux2) abnormal reading detected.

Likely causes

  1. Loose, disconnected, broken or short-circuited connector
  2. Loose connector
  3. Disconnected connector
  4. Broken connector

Where to start

  1. Check connector and wiring of THMaux2
  2. Check THMaux2 thermistor connector for looseness, disconnection, breakage or short-circuit

The full answer, free

  • How to put it right, step by step
  • The manual page for this fault (page 336), right under the answer

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 Hitachi manual for the Yutaki M & Yutaki S. Check the model on the data plate before you order parts.

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