U4-65 Low
Your boiler is still providing heat and hot water, but it has lost communication with your smart room thermostat, meaning you cannot control the temperature remotely.
Technical description: OpenTherm room thermostat connection is defective – your boiler will continue to operation but the thermostat is out of operation
Typical repair cost: £80-180 (including labour)
DIY fix possible
Check that your room thermostat has power and functional batteries.Ensure the thermostat bridge or receiver is plugged in and switched on.Inspect the wiring connection between the thermostat wall plate and the boiler for any loose cables.
Protect yourself from future repair bills
A boiler cover plan would cover faults like U4-65 — no call-out fees, no surprises.
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Parts commonly replaced
- OpenTherm Communication Cable
- Smart Thermostat receiver
- Room Thermostat
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