BoilerFaultCodesVaillant F.64 Fault Code
Also written as F64 — same fault.
The Vaillant F.64 fault code means: your boiler has detected an electrical fault within its internal sensors or control board, which has caused the system to shut down for safety.. It appears on 45 Vaillant models in our database.
Technical description: Electronics/sensor fault: Short-circuit in flow or return sensor or electronics defective
What causes the Vaillant F.64 fault?
This fault occurs when the boiler's internal computer receives conflicting or impossible signals from its temperature sensors. It is usually caused by a short circuit in the wiring or a total failure of the NTC sensors that measure water temperature, but it can also indicate that the main control board is no longer processing data correctly. To prevent overheating, the boiler immediately shuts down until the faulty electrical component is replaced.
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.64: no call-out fees, no surprise bills.
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Vaillant models that show the F.64 fault code
Click a model for the full fault code list and model-specific repair notes.
- ecoFIT Pure 412 Repair: £200-450
- ecoFIT Pure 418 Repair: £250-450
- ecoFIT Pure 425 Repair: £250-450
- ecoFIT Pure 435 Repair: £150-350
- ecoFIT pure 612 Repair: £250-450
- ecoFIT pure 615 Repair: £250-450
- ecoFIT pure 618 Repair: £250-450
- ecoFIT pure 630 Repair: £250-450
- ecoFIT Pure 825 Repair: £250-450
- ecoFIT Pure 830 Repair: £200-450
- ecoFIT Pure 835 Repair: £250-450
- ecoFIT sustain 415 Repair: £250-450
- ecoFIT sustain 418 Repair: £250-450
- ecoFIT sustain 430 Repair: £250-450
- ecoFIT sustain 615 Repair: £250-450
- ecoFIT sustain 618 Repair: £250-450
- ecoFIT sustain 630 Repair: £250-450
- ecoFIT sustain 825 Repair: £250-450
- ecoFIT sustain 830 Repair: £250-450
- ecoFIT sustain 835 Repair: £250-450
- ecoMAX Repair: £180-450
- ecoMAX 613 Repair: £120-£450
- ecoMAX 618 Repair: £120-£450
- ecoMAX 622 Repair: £120-£450
- ecoMAX 635 Repair: £120-£450
- ecoMAX 824/2 E Repair: £120-£450
- ecoMAX 828/2 E Repair: £120-£450
- ecoMAX 835 E Repair: £120-£450
- Ecomax Condensing 600/800 series Repair: £250-450
- ecoTEC exclusive Repair: £120-£450
- ecoTEC plus Repair: £120-450
- ecoTEC plus VU GB 656/4-5 A Repair: £250-450
- ecoTEC pro Repair: £140-450
- ecoTEC sustain Repair: £180-450
- Home Combi 25 Repair: £250-450
- Home Combi 30 Repair: £250-450
- Home Combi 35 Repair: £250-450
- Home Regular 12
- Turbomax 824/828 Repair: £150-£300
- Turbomax Plus Repair: £150-300
- Turbomax Plus 824/828E Repair: £180-450
- Turbomax Plus 828 Repair: £120-£450
- Turbomax Plus 828 E Repair: £180-450
- Turbomax Plus VUW 242E Repair: £180-450
- Turbomax Plus VUW 242EH Repair: £180-450
Source
Vaillant F.64 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