Low
AP073 on Baxi 400 Combi 2

Your boiler is noting the outdoor temperature to decide whether to turn your heating on, which is a normal status update rather than a system fault.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Monitor it

This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.

What the manual says

Manufacturer manual

Average external temperature [°C] when switching from summer/winter mode (with outside sensor)

From this model's manual
Verified against the Baxi 400 Combi 2 installation & service manual, page 53.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

Engineer required

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

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