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Daikin Altherma fault L3-00

Outdoor unit: electrical box temperature rise problem

Heat pump

What it means

Switch box temperature is too high, causing the unit to stop operating.

Likely causes

  1. Faulty inverter PCB
  2. Faulty outdoor unit fan motor
  3. Faulty or disturbance of the power supply (power supply MUST be within range of nominal operating voltage ±4%)
  4. Power drop
  5. Short circuit
  6. Dirty outdoor heat exchanger

Where to start

  1. Perform a check of the inverter PCB
  2. Perform a check of the outdoor unit fan motor
  3. Check if the power supply is compliant with the regulations per section 4.1 Electrical circuit

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 55), 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