Display shows A13; water heater indicates sensor fault on solar coil or additional heat source coil.

Safety first: Turn off power before accessing sensor wiring or control boards.

This alarm relates to the temperature sensor on an auxiliary coil (e.g. solar thermal coil) in the Nibe cylinder.

• Step 1 – Identify coil sensor:
  • Refer to the wiring diagram to locate the sensor assigned to the auxiliary coil.
• Step 2 – Inspect installation:
  • Ensure the sensor is fully inserted into the correct sensor pocket on the coil connection.
  • Check that it is not swapped with another sensor.
• Step 3 – Wiring and test:
  • Inspect the cable for damage and reseat the connector.
  • Measure resistance and compare to expected values.
• Step 4 – Reset:
  • Restore power, clear the alarm, and verify that the coil temperature reading is stable.

Replace the sensor if faulty; if the alarm persists, the control input may be defective.