BoilerFaultCodesVaillant F.76 Fault Code
Also written as F76 — same fault.
The Vaillant F.76 fault code means: your boiler has shut down because a safety sensor has detected that the main heating component is getting too hot or has a broken internal fuse.. It appears on 16 Vaillant models in our database.
Technical description: Overheating protection on primary heat exchanger triggered | Cable or cable connection of fuse in the primary heat exchanger defective, or primary heat exchanger defective
What causes the Vaillant F.76 fault?
This fault occurs when a dedicated safety fuse inside the main heat exchanger has melted or 'tripped' to prevent the boiler from melting down. It is triggered when the heat exchanger becomes dangerously hot, often due to a lack of water flow, a severe blockage, or a build-up of air inside the central heating system. Once this fuse has blown, it is a hardware failure that prevents the boiler from firing up for safety reasons.
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.76 fault code
Click a model for the full fault code list and model-specific repair notes.
- Atmomax Repair: £250-£650
- ecoFIT Pure 412 Repair: £150-350
- ecoFIT Pure 418 Repair: £150-300
- ecoFIT Pure 425 Repair: £150-300
- ecoFIT Pure 435 Repair: £150-300
- ecoFIT Pure 825 Repair: £150-350
- ecoFIT Pure 830 Repair: £150-300
- ecoFIT Pure 835 Repair: £150-300
- ecoTEC Repair: £150-£650
- ecoTEC Plus 615 Repair: £450-900
- ecoTEC Plus 620 Repair: £450-900
- ecoTEC Plus 625 Repair: £450-900
- ecoTEC Plus 630 Repair: £450-900
- ecoTEC Plus 635 Repair: £450-900
- ecoTEC Plus 840 Repair: £450-900
- ecoTEC Pro / ecoTEC Plus Repair: £180-600
Source
Vaillant F.76 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 manual (PDF)
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026