BoilerFaultCodesVaillant F.00 Fault Code
Also written as F00 — same fault.
The Vaillant F.00 fault code means: your boiler has lost connection with its internal temperature sensor, meaning it cannot monitor heat levels and has shut down as a safety precaution.. It appears on 34 Vaillant models in our database.
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 the Vaillant F.00 fault?
This fault occurs when the boiler's main control board loses communication with the temperature sensor that monitors the water leaving the unit. The most common reason is that the sensor itself has failed due to age or internal wear, though it can also be caused by loose wiring or water damage to the electrical connections inside the casing.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
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A cover plan would handle faults like F.00: no call-out fees, no surprise bills.
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Vaillant models that show the F.00 fault code
Click a model for the full fault code list and model-specific repair notes.
- ecoFIT Pure 412 Repair: £120-200
- ecoFIT Pure 418 Repair: £120-200
- ecoFIT Pure 425 Repair: £120-200
- ecoFIT Pure 435 Repair: £120-220
- ecoFIT pure 612 Repair: £120-220
- ecoFIT pure 615 Repair: £120-220
- ecoFIT pure 618 Repair: £120-220
- ecoFIT pure 630 Repair: £120-220
- ecoFIT Pure 825 Repair: £120-220
- ecoFIT Pure 830 Repair: £150-250
- 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: £120-220
- ecoFIT sustain 618 Repair: £120-220
- ecoFIT sustain 630 Repair: £120-220
- ecoFIT sustain 825 Repair: £120-220
- ecoFIT sustain 830 Repair: £120-220
- ecoFIT sustain 835 Repair: £120-220
- ecoTEC plus
- ecoTEC pro Repair: £90-160
- ecoTEC sustain Repair: £90-160
- Home Combi 25 Repair: £120-220
- Home Combi 30 Repair: £120-220
- Home Combi 35 Repair: £120-220
- 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: £90-160
- Turbomax Plus 828 E Repair: £90-160
- Turbomax Plus VUW 242E Repair: £90-160
- Turbomax Plus VUW 242EH Repair: £90-160
Source
Vaillant F.00 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