How much does it cost to fix Baxi error code H.03 -.00?

Typical repair cost for the Baxi H.03 -.00 fault is £90-180 including labour.

H.03 -.00 High

Baxi H.03 -.00 Fault Code

Q: What does the Baxi H.03 -.00 fault code mean?

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

Also written as H0300 — same fault.

The Baxi H.03 -.00 fault code means: your boiler has stopped working because its internal sensors or control system are struggling to talk to each other correctly.. It appears on 24 Baxi models in our database.

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 the Baxi H.03 -.00 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.

Typical repair cost £90-180 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Baxi models that show the H.03 -.00 fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Baxi H.03 -.00 fault code information on this page is sourced and cross-checked against the official Baxi service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026