BoilerFaultCodesYour boiler has stopped working because it can no longer accurately measure the temperature of the water leaving the unit due to a sensor or wiring 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: NTC broken; NTC cable broken; Defective connection at NTC Defective connection at electronics | Flow-NTC cable defective/ broken NTC faulty
What causes this fault?
This fault occurs when the boiler's main control board loses communication with the sensor that monitors the temperature of the water exiting the unit. The most common reason is that the internal sensor has developed an electrical failure or the thin wiring connecting it to the main circuit board has become loose or damaged.
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.00 — no call-out fees, no surprises.
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Vaillant Thermocompact 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.
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