Vaillant Control Signal / Thermostat Communication Fault

Boiler will not respond to room thermostat, heating stays off or on permanently

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

Faulty Vaillant eBUS room controller, Broken thermostat wiring, Incorrect wiring at boiler terminals, PCB input fault

Safety: Isolate power before accessing wiring terminals.

User checks:

Verify that the room thermostat or Vaillant controller has power and is set to call for heat.
Replace batteries in wireless thermostats if applicable.

Professional checks:

Test continuity of thermostat wiring and repair any breaks.
Check correct connection of eBUS or 230V controls at the boiler.
Temporarily bridge the heating demand terminals at the boiler to see if it responds (qualified person only).
Replace faulty thermostat or PCB input as required.

Medium 3/5

Room Thermostat / Vaillant eBUS Controller

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