BoilerFaultCodesYour boiler has detected a problem with the temperature sensor that monitors the water returning from your radiators, causing it to stop heating for safety.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Return–NTC: – NTC broken – NTC cable broken – Defective connection at NTC – Defective connection at electronics | Return–NTC cable defective/broken NTC faulty
What causes this fault?
This fault occurs when the piece of equipment responsible for measuring the temperature of the water returning to the boiler stops sending a clear signal. This is usually caused by the internal sensor failing due to age or a loose electrical connection in the wiring that links the sensor to the boiler's main control board.
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.
Gas Safe Register →Protect yourself from future repair bills
A boiler cover plan would cover faults like F.1 — no call-out fees, no surprises.
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