BoilerFaultCodesVaillant F.01 Fault Code
Also written as F01 — same fault.
The Vaillant F.01 fault code means: your boiler has stopped working because one of its internal temperature sensors is not communicating correctly with the main control board.. It appears on 34 Vaillant models in our database.
Technical description: Return NTC: NTCbroken; NTCcable broken; Defective connection at NTC Defective connection at electronics | Return-NTC cable defective/broken NTC faulty
What causes the Vaillant F.01 fault?
This fault occurs when the boiler's main control board loses communication with the sensor that monitors the temperature of the water leaving the unit. The most common reasons are an electrical failure within the sensor itself or a break in the wiring caused by vibration, heat exposure, or moisture. Without this 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.
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A cover plan would handle faults like F.01: no call-out fees, no surprise bills.
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Vaillant models that show the F.01 fault code
Click a model for the full fault code list and model-specific repair notes.
- ecoFIT Pure 412 Repair: £120-220
- ecoFIT Pure 418 Repair: £120-200
- ecoFIT Pure 425 Repair: £120-200
- ecoFIT Pure 435 Repair: £120-220
- ecoFIT pure 612 Repair: £90-180
- ecoFIT pure 615 Repair: £90-180
- ecoFIT pure 618 Repair: £90-180
- ecoFIT pure 630 Repair: £90-180
- ecoFIT Pure 825 Repair: £120-220
- ecoFIT Pure 830 Repair: £120-220
- ecoFIT Pure 835 Repair: £120-200
- ecoFIT sustain 415 Repair: £120-220
- ecoFIT sustain 418 Repair: £120-220
- ecoFIT sustain 430 Repair: £120-220
- ecoFIT sustain 615 Repair: £90-180
- ecoFIT sustain 618 Repair: £90-180
- ecoFIT sustain 630 Repair: £90-180
- ecoFIT sustain 825 Repair: £90-180
- ecoFIT sustain 830 Repair: £90-180
- ecoFIT sustain 835 Repair: £90-180
- ecoTEC plus Repair: £120-220
- ecoTEC pro Repair: £90-160
- ecoTEC sustain Repair: £100-£180
- Home Combi 25 Repair: £120-200
- Home Combi 30 Repair: £120-200
- Home Combi 35 Repair: £120-200
- Home Regular 12
- Turbomax 824/828 Repair: £120-220
- Turbomax Plus Repair: £120-220
- Turbomax Plus 824/828E Repair: £90-160
- Turbomax Plus 828 Repair: £120-220
- Turbomax Plus 828 E Repair: £90-160
- Turbomax Plus VUW 242E Repair: £90-160
- Turbomax Plus VUW 242EH Repair: £90-160
Source
Vaillant F.01 fault code information on this page is sourced and cross-checked against the official Vaillant service / installation manuals for each affected model.
- Vaillant ecoFIT Pure 425 manual (PDF)
- Vaillant ecoFIT Pure 435 manual (PDF)
- Vaillant ecoFIT pure 630 manual (PDF)
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 31 August 2026