How to fix Worcester Bosch Greenstar Si fault code F84

What does the Worcester Bosch Greenstar Si F84 fault code mean?

The F84 fault code on the Worcester Bosch Greenstar Si indicates a safety issue within the heating system, typically related to the pressure or flow of water. This fault can prevent the boiler from operating safely, requiring immediate attention.

Common Causes

  • Low Water Pressure: Insufficient water pressure can trigger the F84 fault, as the system requires a certain level to function correctly.
  • Blocked or Faulty Components: Issues such as a blocked heat exchanger or faulty pump can disrupt the flow of water, leading to safety concerns.

Can I fix it myself? (DIY)

It is advisable to check the water pressure and reset the boiler if it is low. However, for any gas or electrical issues, you must call a qualified Gas Safe Engineer to ensure safety and compliance with regulations.

Estimated Repair Cost (2026 UK Prices)

The estimated repair cost for resolving the F84 fault could range from £150 to £300, depending on whether it involves a simple pressure adjustment or the replacement of faulty components like the pump or heat exchanger.