BoilerFaultCodesYour boiler has detected a communication problem or a fault with the sensor that controls your central heating temperature.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Check the CH sensor and panel control and/or the wires connecting them to the PCB.
What causes this fault?
This fault occurs when the boiler's main computer loses touch with the sensor that monitors your heating water temperature. It usually happens because the sensor has failed internally or the electrical wires connecting it to the control board have become loose or damaged. Without this vital temperature data, the boiler shuts down as a safety precaution to prevent overheating.
This fault often appears when the heating is first turned on in autumn, as the sudden change in temperature can cause aging electrical sensors to fail.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
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A boiler cover plan would cover faults like CH light on PCB 40 flashing — no call-out fees, no surprises.
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