BoilerFaultCodesYour boiler has lost its digital connection with your external smart thermostat or heating controls, meaning it cannot receive instructions to turn on.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: OpenTherm communication error
What causes this fault?
This fault occurs when the digital 'conversation' between your boiler and your smart thermostat is interrupted, leaving the boiler without instructions. The most common reasons are a loose connection in the control wiring, a software glitch in the thermostat unit, or a complete failure of the communication module inside the boiler.
DIY fix possible
Check that your external thermostat or wall control is powered on and has fresh batteriesEnsure the wires connecting your thermostat to the boiler haven't been accidentally bumped or damagedTurn the boiler off at the main power switch, wait 30 seconds, and turn it back on to reset the connection
Find a Gas Safe engineer
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A boiler cover plan would cover faults like E31 — no call-out fees, no surprises.
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Parts for discontinued models can be hard to find and expensive. A new A-rated boiler could save you money on both repairs and energy bills.
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