Thermostat does not power on at all; display is blank and app cannot find the device.
Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
Possible Causes
How to Fix / Troubleshooting
Safety first: Always turn off the main breaker before removing the thermostat from the wall. Use a non-contact tester to confirm power is off.
Steps:
- Check breaker and fuse: Locate the heating/thermostat circuit breaker and ensure it is ON. Reset if tripped. If it trips again immediately, there is a short that must be found before proceeding.
- Verify supply at wall plate: Remove the thermostat and, with power restored, measure voltage between L and N on the backplate. If no voltage is present, trace wiring back to the junction box or boiler and repair the supply.
- Inspect terminals: Turn power off again. Confirm that the live and neutral conductors are firmly clamped and not broken at the thermostat.
- Test thermostat on known-good supply: If possible, temporarily connect the thermostat to a known-good mains feed. If it still does not power on, the internal power supply is defective.
Resolution: Restore proper supply wiring or replace the thermostat if internal electronics have failed.
Repair Difficulty
Required Part
We may earn a commission from links on this page.