BoilerFaultCodesVaillant F.70 Fault Code
Also written as F70 — same fault.
The Vaillant F.70 fault code means: your boiler’s internal computer boards are having trouble communicating because they haven't been properly synced or configured to recognize each other.. It appears on 29 Vaillant models in our database.
Technical description: No valid appliance variant for display and/or electronics: Spare part case: Display and electronics changed at the same time appliance variant not re-set
What causes the Vaillant F.70 fault?
This fault occurs when the boiler's internal control boards fail to recognize the specific model they are installed in, often because the 'identity code' has been lost or not set. This usually happens after a physical repair where both the main circuit board and the display screen were replaced simultaneously, leaving the system without a master record of its own configuration. Without this data, the boiler enters a safety mode because it doesn't know its own power rating or technical specifications.
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.70 fault code
Click a model for the full fault code list and model-specific repair notes.
- ecoFIT Pure 412 Repair: £150-300
- ecoFIT Pure 418 Repair: £120-250
- ecoFIT Pure 425 Repair: £120-250
- ecoFIT Pure 435 Repair: £90-150
- ecoFIT pure 612 Repair: £120-250
- ecoFIT pure 615 Repair: £120-250
- ecoFIT pure 618 Repair: £120-250
- ecoFIT pure 630 Repair: £120-250
- ecoFIT Pure 825 Repair: £150-300
- ecoFIT Pure 830 Repair: £150-300
- ecoFIT Pure 835 Repair: £120-250
- ecoFIT sustain 415 Repair: £150-300
- ecoFIT sustain 418 Repair: £150-300
- ecoFIT sustain 430 Repair: £150-300
- ecoFIT sustain 615 Repair: £120-250
- ecoFIT sustain 618 Repair: £120-250
- ecoFIT sustain 630 Repair: £120-250
- ecoFIT sustain 825 Repair: £120-250
- ecoFIT sustain 830 Repair: £120-250
- ecoFIT sustain 835 Repair: £120-250
- ecoTEC exclusive Repair: £90-180
- ecoTEC plus Repair: £120-450
- ecoTEC plus VU GB 656/4-5 A Repair: £150-300
- ecoTEC pro Repair: £100-£350
- ecoTEC sustain Repair: £100-£350
- Home Combi 25 Repair: £150-300
- Home Combi 30 Repair: £150-300
- Home Combi 35 Repair: £150-300
- Home Regular 12
Source
Vaillant F.70 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