High Lockout
H.03 -.00 on Baxi 200 Combi (range)

Your boiler has stopped working because its internal sensors or control system are struggling to talk to each other correctly.

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

Temporary error with communication, negative temperature coefficient thermostat (NTC) or flue sensor. Sensor could also be unconnected or have a bad connection.

What causes this fault?

This fault happens when the boiler's main control board loses touch with the sensors that monitor heat levels. It is usually caused by a faulty temperature sensor providing an impossible reading or a loose wire preventing the components from 'talking' to each other. When the brain of the boiler isn't sure how hot the water or exhaust gases are, it shuts down as a safety precaution.

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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