Your boiler may display the Worcester A8 error code if it loses communication with the FX sensor. This usually points to a fault with the sensor itself or the wiring connected to it. While a reset may clear a temporary issue, a recurring fault should be checked by a qualified engineer.
What does the Worcester A8 error code mean?
The A8 error code indicates that the boiler can no longer communicate correctly with the FX sensor.
The FX sensor helps monitor boiler operation. If communication is interrupted, the boiler may enter a fault condition to protect the system until the problem is resolved.
Common causes of the Worcester A8 fault
Faulty FX sensor
The FX sensor may have failed internally, preventing it from sending information to the boiler controls.
Damaged wiring
A damaged, loose or broken wiring connection between the boiler and the FX sensor can also trigger the A8 error.
Can you reset the A8 error?
A reset can sometimes clear a temporary communication fault.
- Switch the boiler off.
- Wait for the period recommended in the Worcester Bosch manual.
- Turn the boiler back on.
- Check whether the fault code has cleared.
If the A8 error returns, avoid repeatedly resetting the boiler. An ongoing fault usually means the sensor or its wiring needs further inspection.
If you're seeing a different fault code, our guide to Worcester Bosch fault codes explains many of the most common error messages.
When you should call a Gas Safe engineer
Because this fault involves internal electrical components and boiler controls, diagnosis should be carried out by a qualified Gas Safe engineer.
The engineer can test the FX sensor, inspect the wiring and confirm whether replacement parts are required.
If the A8 error keeps returning or your boiler has stopped working, our boiler repair service in London can diagnose the fault and carry out the necessary repair.
Preventing future boiler faults
Some faults cannot be avoided, but regular servicing helps identify worn parts before they fail.
An annual boiler service also checks the appliance's safety and efficiency, helping reduce the chance of unexpected breakdowns.
