BoilerFaultCodesYour boiler has lost connection with its main internal temperature sensor, meaning it cannot safely tell how hot the water is and has shut down as a precaution.
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: NTC broken, NTC cable broken, Defective connection at NTC, Defective connection at electronics | Cause: Flow–NTC cable defective/broken NTC faulty
What causes this fault?
This fault occurs when the boiler's internal computer can no longer detect a signal from the sensor that monitors water temperature. The most common reason is that the sensor itself has simply worn out over time, though it can also be caused by a loose connection or damaged wiring inside the unit.
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.
Vaillant Ecomax 613 2 E is discontinued — time for a new one?
Parts for discontinued models can be hard to find and expensive. A new A-rated boiler could save you money on both repairs and energy bills.
Affiliate links — we may earn a commission at no extra cost to you.