BoilerFaultCodesYour boiler has detected that its internal temperature sensors are either misaligned or not communicating correctly, preventing the system from heating safely.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Error with flow and return temperature, sensor incorrectly fitted
What causes this fault?
This fault occurs when the boiler detects that its internal temperature sensors are not responding in the way they should, often because they have come loose or were installed incorrectly. The most common reason is that a sensor has shifted away from the pipework it is meant to monitor, meaning it cannot provide an accurate reading to keep the system running safely.
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 F.85 — no call-out fees, no surprises.
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Could it be time for a new boiler?
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