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Witten by Bernard Morgan (Engineer) & Adam Apperley (Marketing). Published: February 7, 2024. Updated: May 17, 2024

F76 Vaillant Error Code – How to fix

The Vaillant boiler F76 fault code indicates an overheated boiler engine. This often leads to automatic shutdown for safety. This serious fault may necessitate professional repairs or possibly a whole new boiler.

Understanding F76

Triggered by excessive heat exchanger temperatures, the F76 fault code is a warning of an overheating boiler. A thermal fuse that monitors and responds to dangerous temperature levels initiates an automatic shutdown. This prevents further damage or hazards.

Causes of Overheating

Several factors can lead to an F76 fault. These include trapped air in the heat exchanger, wiring issues, faulty temperature sensors, and physical blockages. Each of these problems can disrupt normal operation and lead to overheating.

Professional Intervention Required

Due to the complexity and potential dangers of addressing an F76 fault, DIY repairs are not advisable. A Gas Safe registered professional must be enlisted to diagnose and rectify the issue safely and in compliance with legal requirements.

Deciding on Repairs or Replacement

The decision to repair or replace a boiler following an F76 fault depends on the specific cause and the overall condition of the boiler. In cases where the heat exchanger is at fault, replacement costs can be significant, prompting considerations for a new boiler installation.

Cost Estimates

The cost of resolving an F76 error varies widely, influenced by the severity of the issue and geographic location. Specific repairs may range from £200 to £1,000, while replacing a heat exchanger can cost between £640 and £1,500. A new boiler cost is between £2,100 and £3,400.


In summary, the F76 fault code signifies a severe issue requiring prompt and professional attention. Understanding the potential causes and associated costs can help you make informed decisions about their next steps.

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