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 28 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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Vaillant models that show the F.01 fault code
Click a model for the full fault code list and model-specific repair notes.
- Atmomax Repair: £90-160
- ecoFIT Pure 412 Repair: £120-220
- ecoFIT Pure 418 Repair: £120-200
- ecoFIT Pure 425 Repair: £120-200
- ecoFIT Pure 435 Repair: £120-200
- ecoFIT Pure 825 Repair: £120-220
- ecoFIT Pure 830 Repair: £120-220
- ecoFIT Pure 835 Repair: £120-200
- ecoTEC exclusive Repair: £120-220
- ecoTEC Plus 610 Repair: £120-220
- ecoTEC Plus 826 Repair: £120-£200
- ecoTEC Plus 938 Repair: £100-£180
- ecoTEC plus aquaPLUS Repair: £90-180
- ecoTEC Pro Repair: £90-160
- ecoTEC Pro 24 Repair: £90-160
- ecoTEC Pro 28 Repair: £90-160
- ecoTEC Pro 30 Repair: £120-220
- ecoTEC sustain Repair: £100-£180
- Home Combi Repair: £120-200
- Home System Repair: £90-180
- Thermocompact Repair: £90-180
- 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 412 manual (PDF)
- Vaillant ecoFIT Pure 835 manual (PDF)
- Vaillant ecoTEC exclusive manual (PDF)
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026