BoilerFaultCodesYour boiler's temperature sensors are receiving conflicting or incorrect readings, causing the system to stop working correctly to protect itself.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Low loss header temperature sensor faulty – check the sensor port or check the differential sensor for incorrect installation position or breakage
What causes this fault?
This fault occurs when the boiler's control system detects a discrepancy between the water temperature sensors, often because the sensor monitoring the external mixing point is giving an impossible reading. The most common reasons are a physical failure of the sensor itself, an electrical fault in the connecting wires, or the sensor being installed in the wrong location during a complex system setup.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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A boiler cover plan would cover faults like 815 W/B — no call-out fees, no surprises.
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Could it be time for a new boiler?
If repair costs are adding up, a new energy-efficient boiler could be the smarter long-term choice.
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