High Lockout
437 on Ideal Ideal Classic SE15P FF

Your boiler has stopped working because a sensor that monitors water temperature has lost its connection or stopped sending information.

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

NTC2 open

What causes this fault?

This fault occurs when the boiler's control board loses communication with the sensor that monitors the temperature of the water leaving the unit. The most common reason is that the sensor has internal electrical failure or the wiring connecting it to the main board has become loose or damaged. Without this data, the boiler shuts down as a safety precaution because it cannot verify if the water is getting too 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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