High Lockout
H.....4...... on Ideal Mexico HE

Your boiler has detected that a safety sensor in the flue pipe is reporting an incorrect temperature reading.

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

FLUE THERMISTOR ERROR

What causes this fault?

This fault occurs when the boiler's control board receives an impractical temperature reading from the sensor located in the exhaust flue. It usually happens because the sensor has failed internally or the electrical wiring connecting it to the main board has become damaged or loose. Because this sensor is a critical safety component designed to prevent the boiler from overheating, the system will shut down immediately to prevent damage.

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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