Glow-worm
No Power to Thermostat
Thermostat display completely dead, no lights or response
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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.
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Possible Causes
Flat or incorrectly fitted batteries, No 24 V/230 V supply to thermostat backplate, Loose connection at wiring center, Blown internal fuse in receiver/backplate
How to Fix / Troubleshooting
Safety: If your thermostat or receiver is mains powered, isolate power at the fused spur before removing covers. Battery replacement is safe with power on.
Steps:
- If the thermostat is battery powered, remove the cover, replace all batteries with new high‑quality alkaline cells, and ensure correct polarity.
- For mains/24 V powered models, check that the boiler and wiring center are powered and that any local isolator switches are ON.
- Remove the thermostat from its backplate and inspect the contact pins for corrosion or bent contacts. Clean gently and refit.
- At the wiring center or receiver (with power isolated), check that the supply live and neutral are present and that any small internal fuses are intact. Replace fuses only with the specified rating.
Remedy:
- If correct power is present at the backplate but the thermostat remains dead, the thermostat PCB is likely failed. Replace the thermostat head.
- If no power reaches the backplate, trace and repair the supply wiring or replace the faulty transformer/receiver.
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Repair Difficulty
Medium
3/5
Required Part
Glow-worm smart thermostat head or powered backplate
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