BoilerFaultCodesWorcester Bosch 1-A6 Fault Code
Also written as 1A6 — same fault.
The Worcester Bosch 1-A6 fault code means: your boiler is receiving a command from your smart thermostat or heating controller that it cannot currently process, often due to a communication glitch or a sensor reading incompatibility.. It appears on 1 Worcester Bosch model in our database.
Technical description: Set flow temperature: Setting value of the flow temperature demanded by the heating controller.
What causes the Worcester Bosch 1-A6 fault?
This fault happens when the boiler and your smart thermostat stop speaking the same language, usually because the controller is asking for a water temperature that the boiler cannot safely provide. It is often caused by a temporary communication glitch between the wireless receiver and the main control board, or a sensor that is sending inconsistent data. Essentially, the boiler has received an instruction it doesn't understand, so it pauses that specific command to protect itself.
DIY fix possible
Check that your room thermostat or smart hub is powered on and has batteriesTurn your boiler off and on again using the power button to reset the communication linkEnsure your smart heating schedule is not requesting an impossibly high temperature
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Gas Safe Register →Worcester Bosch models that show the 1-A6 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Worcester Bosch 1-A6 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