Worcester Bosch F7 Fault

Worcester Bosch F7 Fault

The Worcester Bosch F7 fault code typically indicates a flame detection issue, suggesting that the boiler’s ignition system has detected a flame signal when it shouldn’t have, such as before ignition has been officially initiated. This could be caused by a range of issues related to the boiler’s ignition process or flame sensing components. Here’s a more detailed look at potential causes and solutions for the F7 fault code:

Causes of the F7 Fault Code

  1. Faulty Flame Detection Sensor: The flame detection sensor, responsible for detecting whether the burner has ignited, might be faulty or dirty, causing it to incorrectly sense a flame.
  2. Control Board Issues: The boiler’s printed circuit board (PCB) controls the operation of the boiler, including the ignition process. A malfunction in the PCB could result in erroneous signals, like detecting a flame when there is none.
  3. Electrical Interference: External electrical interference or a short circuit within the boiler’s electrical components could potentially lead to false flame detection.
  4. Burner Problems: Issues with the burner, such as residual gas or an actual lingering flame from a previous cycle, could falsely trigger the flame detection sensor.

Troubleshooting and Resolving the F7 Fault Code

  1. Inspect and Clean the Flame Detection Sensor: Over time, the flame detection sensor can become dirty or corroded, impairing its function. Cleaning or replacing the sensor can often resolve the issue.
  2. Check Wiring and Electrical Connections: Inspect the wiring connections to the flame detection sensor and PCB for signs of damage, corrosion, or loose connections that could cause false readings.
  3. Reset the Boiler: Attempting to reset the boiler can sometimes clear transient faults. If the F7 code persists after a reset, further investigation is needed.
  4. Inspect the Burner: Check the burner for any issues that could cause a flame to be detected erroneously. This might include cleaning the burner or adjusting its settings.
  5. Consult a Gas Safe Registered Engineer: Because dealing with boiler electrical components and gas burners can be complex and potentially hazardous, it’s advisable to have a qualified professional diagnose and repair the issue. A Gas Safe registered engineer can assess the entire ignition system and make the necessary repairs or replacements.
  6. Consider PCB Assessment: If the issue is not resolved by addressing the sensor, wiring, or burner, the problem might lie with the PCB itself. A professional can test the PCB and replace it if necessary.


The Worcester Bosch F7 fault code is a serious issue that indicates a problem with flame detection, requiring prompt attention. While some preliminary checks and a reset can be attempted by the homeowner, most solutions involve technical assessments and repairs best carried out by a Gas Safe registered engineer. Regular maintenance and servicing can help prevent issues like the F7 fault by ensuring that the boiler’s components are in good condition and functioning correctly.