Error 42 (4 Green, 2 Red Flashes) — Hydraulic unit heat-exchange thermistor Error

What does 42 mean?

The hydraulic unit's green LED flashes four times and the red LED flashes twice. This indicates a fault with the heat-exchange thermistor located within the hydraulic unit.

• The heat-exchange thermistor is faulty or has failed.
• Loose or corroded connection to the thermistor.
• Damage to the thermistor wiring.

Click steps to track your progress.

1. 1

   Restart the heat pump system by switching off the main power for one minute and then switching it back on.

2. 2

   Check the system's display for any further information about the thermistor error.

3. 3

   Ensure that there are no obvious obstructions around the hydraulic unit that could affect sensor readings.

4. 4

   If you have access, check the connections to the heat-exchange thermistor for looseness (with power off).

5. 5

   Contact a qualified technician to test or replace the heat-exchange thermistor.