Worcester Bosch External Controls / Communication Fault

Boiler does not respond to room thermostat or programmer, stays off even when heat is requested.

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 room thermostat, Flat batteries in wireless thermostat, Faulty receiver or wiring to boiler, Incorrect control wiring at boiler terminals

Safety first: Isolate power before accessing wiring terminals.

Check thermostat settings: Ensure the thermostat is set above room temperature and in HEAT mode.
Replace batteries: For wireless stats, fit new high-quality batteries and re-pair with the receiver if necessary.
Check programmer: Confirm heating channels are set to ON or timed appropriately.
Engineer tasks: An engineer or electrician should test for a call-for-heat signal at the boiler control terminals (e.g. LR/LS), check wiring, and replace faulty controls.

Medium 3/5

Room Thermostat / Control Receiver

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