BoilerFaultCodesIdeal HW light flashing Fault Code
Also written as HWLIGHTFLASHING — same fault.
The Ideal HW light flashing fault code means: your boiler has detected an electrical fault with the sensor that monitors your hot water temperature, meaning it cannot heat water safely.. It appears on 1 Ideal model in our database.
Technical description: Indicates an 'open circuit' or 'short circuit' HW sensor or lead.
What causes the Ideal HW light flashing fault?
This fault occurs when the internal sensor responsible for tracking the temperature of your hot water fails to send a clear signal to the main control board. The most common reason is that the sensor has physically degraded over time or a wire has shaken loose, preventing the boiler from knowing how hot the water is. For safety, the boiler stops heating immediately to prevent the water from becoming dangerously hot.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Gas Safe Register →Ideal models that show the HW light flashing fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Ideal HW light flashing fault code information on this page is sourced and cross-checked against the official Ideal service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026