If your Worcester Bosch boiler is displaying the FA 306 error code, it has detected a flame signal when there isn't actually a flame present. This is known as a false flame fault and usually points to a component that needs professional attention.
The fault is commonly linked to either the air-to-gas ratio control valve or the ionisation cable. While you can safely try a boiler reset, ongoing faults should always be investigated by a Gas Safe engineer.
If your boiler is displaying a different fault, see our guide to Worcester Bosch boiler fault codes for explanations of other common error codes.
What does the Worcester FA 306 error code mean?
The Worcester FA 306 error code appears when the boiler's control system detects a flame signal even though no flame exists.
This usually indicates a fault within the flame detection system rather than an actual ignition problem. Once diagnosed, the issue should be repaired promptly to keep the boiler operating safely.
Common causes of the FA 306 fault
Faulty air-to-gas ratio control valve
The air-to-gas ratio control valve regulates the correct mixture of gas and air during combustion.
If it develops a fault, the boiler may incorrectly register a flame signal. Diagnosing and replacing this component requires specialist equipment and should only be carried out by a qualified Gas Safe engineer.
Damaged ionisation cable
The ionisation cable monitors whether a flame is present.
If the cable becomes loose, damaged or worn, it can send incorrect signals to the boiler's control board and trigger the FA 306 fault. A Gas Safe engineer can inspect the cable and replace it if necessary.
How to troubleshoot the FA 306 error code
Reset the boiler
Start by resetting the boiler using the reset button on the control panel.
A reset can clear temporary faults and restore normal operation. If the FA 306 error returns shortly afterwards, the fault is unlikely to resolve without repair.
Only reset the boiler if you're confident using the controls. If you're unsure, leave the appliance switched off and arrange an inspection.
When to stop troubleshooting
If the fault keeps returning after a reset, avoid repeated resets.
Persistent FA 306 faults usually indicate a failed component that needs professional diagnosis rather than repeated restarting.
When to call a Gas Safe engineer
If the Worcester FA 306 error code remains after a reset, arrange an inspection by a qualified Gas Safe engineer.
The engineer can test the flame detection system, inspect the air-to-gas ratio valve and ionisation cable, and replace any faulty components safely.
If the FA 306 fault keeps returning after a reset, it's best to arrange a professional boiler repair in London before the problem gets worse. Ignoring the fault could lead to repeated boiler lockouts and unreliable heating.
