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Mitsubishi Ecodan fault L5

Flow/return/tank/zone water temperature thermistor failure

Heat pump

What it means

Error code displayed when one of THW1, THW2, THW5, THW6, THW7, THW8, or THW9 is at open or short circuit. Open detection at -39ºC or below, short detection at 88.5ºC or above.

Likely causes

  1. Failed thermistor TH1A, TH2, THW1, THW2, THWB1, THW5, THWB2, TH1B, THW6, THW7, THW8, or THW9
  2. Connector/terminal wire has become detached or loose wiring
  3. Thermistor fault
  4. FTC board failure
  5. Thermistor on the wireless remote controller or main remote controller may be defective
  6. Incorrect setting of the DIP switch(es)

Where to start

  1. Enter request code 567 to identify the specific failed thermistor
  2. Visually check the terminals and connections and reattach as appropriate
  3. Check resistance of thermistor against table in section 10-6

The full answer, free

  • 3 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 48), 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