C (Flashing) Low

Halstead C (Flashing) Fault Code

Also written as CFLASHING — same fault.

The Halstead C (Flashing) fault code means: your boiler has been manually or accidentally switched into a service testing mode, meaning it is running at a restricted low power level rather than responding to your heating demands.. It appears on 3 Halstead models in our database.

Monitor it

This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.

Technical description: The appliance enters the SERVICE mode (runs at minimum CH output).
Typical repair cost £0-80 (including labour)

DIY fix possible

Locate the selector switch on the front control panel.Ensure the switch is set to the 'Off/Reset' position for a few seconds.Turn the switch back to the 'Heating and Hot Water' position to exit the service mode.

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Halstead models that show the C (Flashing) fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Halstead C (Flashing) fault code information on this page is sourced and cross-checked against the official Halstead service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026