BoilerFaultCodesYour boiler has detected that a temperature sensor is sending a stuck or frozen reading, preventing it from heating your home or water safely.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Constant value feed NTC: Feed NTC faulty
What causes this fault?
This fault occurs when the boiler's internal computer notices that the flow temperature sensor is sending exactly the same temperature reading for too long, even while the burner is firing. The most common reason is that the sensor has physically failed or developed a high resistance, meaning it can no longer detect the actual rise in heat. It can also be caused by a loose connection or damaged wiring preventing the sensor from communicating correctly with the 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.71 — no call-out fees, no surprises.
Affiliate links — we may earn a commission at no extra cost to you.
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.
Affiliate links — we may earn a commission at no extra cost to you.