Glow-worm Control Signal Not Reaching Boiler

Boiler display is on but does not respond to room thermostat or programmer

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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

Faulty room thermostat, Programmer not sending demand, Broken control wiring, Incorrect wiring at boiler terminals

How to Fix / Troubleshooting

Safety: Isolate power before accessing wiring centres or boiler terminals.

  • Check programmer settings: Confirm the heating and/or hot water channels are set to ON and the current time/day is correct.
  • Override test: Use the programmer's manual override or boost function to force heating on and see if the boiler responds.
  • Thermostat test: Turn the room thermostat up to maximum and listen for a click. If no click, the thermostat may be faulty.
  • Engineer tasks:
    • Test continuity of control wiring between thermostat/programmer and boiler.
    • Check for correct links on boiler terminals if using eBUS controls.
    • Replace faulty room thermostat or programmer.

Incorrect wiring can damage the PCB; use a competent person for control wiring changes.

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Repair Difficulty

Medium 3/5

Required Part

Room Thermostat
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