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Mitsubishi Ecodan fault 25

Mechanical noise heard coming from the cylinder unit

Heat pump

What it means

Mechanical noise from the cylinder unit caused by normal heater switching or 3-way valve changing position between DHW and heating mode.

Likely causes

  1. Heaters switching on/off
  2. 3-way valve changing position between DHW and heating mode

Where to start

  1. Turn OFF water supply, drain DHW tank, remove mesh from strainer, clean and replace in strainer
  2. Keep water supply OFF, open hot water taps and check the primary-side expansion vessel charge pressure; top up if necessary (1 bar)
  3. Keep water supply OFF and check the potable vessel charge pressure; top up if necessary (3.5 bar)

The full answer, free

  • 8 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 57), 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 Mitsubishi manual for the Ecodan. Check the model on the data plate before you order parts.

Other Mitsubishi Ecodan fault codes