Worcester Bosch F9 Fault

Worcester Bosch F9 Fault

The Worcester Bosch F9 fault code is a specific error indication that typically points to an issue with the boiler’s printed circuit board (PCB) or a problem related to the power supply. This fault code can manifest due to various reasons, including electrical issues, component failures, or disruptions in the power supply to the PCB. Understanding the underlying causes and appropriate steps for resolution is crucial for addressing this fault effectively.

Causes of the F9 Fault Code

  1. PCB Failure: The most common cause of an F9 fault is a failure or malfunction within the boiler’s printed circuit board. The PCB is integral to the operation of the boiler, managing and coordinating all its functions. Damage or faults in the PCB can disrupt the entire system.
  2. Electrical Issues: Electrical problems, such as short circuits, wiring issues, or power surges, can damage the PCB or affect its ability to function correctly, leading to an F9 fault.
  3. Power Supply Problems: Inconsistent or faulty power supply to the boiler can trigger an F9 fault. This might be due to issues within the home’s electrical system or specific to the connection with the boiler.

Troubleshooting and Resolving the F9 Fault Code

  1. Reset the Boiler: Attempt a reset as an initial step to see if the fault clears. This can sometimes resolve temporary glitches or errors.
  2. Check Power Supply: Ensure that the boiler’s power supply is stable and consistent. Check for any tripped circuits or issues with the home’s electrical panel that could affect the boiler.
  3. Visual Inspection: While detailed inspection and repairs should be left to professionals, you can visually inspect for obvious signs of damage or wear, such as burnt components or damaged wiring, which could indicate the source of the problem.
  4. Call a Gas Safe Registered Engineer: Due to the technical nature of the F9 fault, involving electrical components and potentially the PCB, it’s advisable to seek the assistance of a qualified professional. A Gas Safe registered engineer can safely diagnose and repair issues related to the PCB or the boiler’s electrical system.
  5. Prepare for Possible PCB Replacement: If the issue is indeed with the PCB, it may require replacement. PCB replacements should be performed by a professional, as they involve handling critical components of the boiler’s operating system.


The F9 fault code on a Worcester Bosch boiler indicates a serious issue that often involves the PCB or the power supply to the boiler. Given the complexity and importance of these components, professional diagnosis and repair are essential. Regular maintenance and timely attention to any signs of electrical issues can help prevent such faults from arising, ensuring the efficient and safe operation of your boiler.