BoilerFaultCodesWorcester Bosch 9.A Fault Code
Also written as 9A — same fault.
The Worcester Bosch 9.A fault code means: your boiler's control panel has been set to stay on permanently, which means it isn't following your usual heating schedule or thermostat settings.. It appears on 1 Worcester Bosch model in our database.
Technical description: Operation mode permanent
What causes the Worcester Bosch 9.A fault?
This code appears when the boiler's internal service or manual override mode has been activated, telling the unit to ignore external thermostats. It often happens if a setting was accidentally changed during a service or if the control dial was left in the ‘on’ position rather than being set to follow your timer. Because the boiler is receiving a permanent 'run' signal, it will continue to heat until you manually switch it back to its automatic mode.
DIY fix possible
Locate the main control dial on the front of the boiler.Turn the dial away from the maximum 'permanent on' setting to a lower number or your desired temperature.Check your external thermostat or programmer to ensure it is now back in control of the heating.
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Gas Safe Register →Worcester Bosch models that show the 9.A fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Worcester Bosch 9.A fault code information on this page is sourced and cross-checked against the official Worcester Bosch service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026