Relay Fault
Worcester Bosch
Stuck or failed switching relay in receiver or thermostat
Smart thermostat or receiver shows 'Relay Fault'; heating does not switch on or remains stuck on.
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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
Worn relay contacts from high switching load, PCB track damage around relay, Overheating of receiver module, Manufacturing defect in relay component
How to Fix / Troubleshooting
Safety first: The receiver is mains‑powered. Isolate power at the fused spur before opening any receiver or wiring centre. If unsure, use a qualified electrician or heating engineer.
- Visual inspection: With power off, remove the receiver cover (if user‑serviceable). Look for signs of burning or discoloration around the relay area.
- Check wiring: Ensure live, neutral, and switched live connections are tight and correctly terminated according to the Worcester Bosch wiring diagram.
- Test operation: Restore power and use the thermostat to call for heat. Listen for a click from the receiver relay. No click or continuous click with no boiler response indicates relay or PCB failure.
- Do not attempt relay replacement yourself: Relay replacement requires PCB soldering and safety testing. Replace the entire receiver module via a professional.
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Repair Difficulty
Professional Required
5/5
Required Part
Worcester Bosch RF Receiver Module
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