Baxi · 400 Combi 2.1

H.03.05 boiler fault code

400 Combi 2.1

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What H.03.05 means

Power supply voltage too low.

Gas Safe engineer: If the mains supply is confirmed OK and the code remains, contact a Gas Safe registered engineer.

A boiler fault code alone is not a gas or carbon-monoxide emergency. If you smell gas, a CO alarm sounds, or someone has possible carbon-monoxide symptoms, leave and call 0800 111 999 from outside.

Safe check

Do not repeatedly reset the boiler. Contact a qualified electrician or your electricity supplier about low mains voltage. If the supply is confirmed OK and the code remains, contact a Gas Safe registered engineer.

When to contact an engineer

If the mains supply is confirmed OK and the code remains, contact a Gas Safe registered engineer.

Source and provenance