High Lockout
HW light flashing on Ideal Classic FF

Your boiler has detected an electrical fault with the sensor that monitors your hot water temperature, meaning it cannot heat water safely.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description

Indicates an 'open circuit' or 'short circuit' HW sensor or lead.

What causes this 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 is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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