BoilerFaultCodesWorcester Bosch CH light On Fault Code
Also written as CHLIGHTON — same fault.
The Worcester Bosch CH light On fault code means: your boiler has automatically turned itself off because it is getting too hot, likely due to a flow issue within your heating system.. It appears on 3 Worcester Bosch models in our database.
Technical description: Over temperature shut-down if flow temperature 5°C above set value
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Worcester Bosch models that show the CH light On fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Worcester Bosch CH light On fault code information on this page is sourced and cross-checked against the official Worcester Bosch service / installation manuals for each affected model.
- Worcester Bosch 28 i SI manual (PDF)
- Worcester Bosch 28 Si RSF manual (PDF)
- Worcester Bosch Greenstar 25Si manual (PDF)
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026