BoilerFaultCodesYour boiler has stopped working because it cannot accurately measure the temperature of the water leaving the unit due to a sensor or wiring connection fault.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Flow–NTC open circuit. NTC broken, NTC cable broken, Defective connection at NTC, Defective connection at electronics
What causes this fault?
This fault occurs when the boiler's control system loses the signal from the sensor that monitors the temperature of the water flowing out to your radiators. The most common reason is that the sensor itself has failed internally or the electrical wiring connecting it to the main control board has become loose or damaged. Without this vital temperature data, the boiler shuts down as a safety precaution to prevent overheating.
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.0 — 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.