4.3 High

Baxi 4.3 Fault Code

Also written as 43 — same fault.

The Baxi 4.3 fault code means: your boiler has detected that the water temperature has risen too high and it has shut down automatically to prevent damage.. It appears on 1 Baxi model in our database.

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: Superstative
Typical repair cost £150-250 (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 4.3 fault code

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

Source

Baxi 4.3 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 7 July 2026