Common problems guide

The most common Baxi 424 COMBI 2.1 problems

The faults most likely to send a Baxi 424 COMBI 2.1 into lockout — with plain-English causes, what to check first, estimated repair costs and whether you need a Gas Safe engineer.

The 6 most common faults

01

H.02.07 Engineer

Low pressure in heating circuit (permanently)

Full guide for H.02.07

02

H.03.02 Engineer

Temporary flame loss

Full guide for H.03.02

03

H.01.05 Engineer

Maximum temperature difference value between flow and return reached.

Full guide for H.01.05

04

E.04.10 Engineer

Burner failed to ignite after 4 attempts

Full guide for E.04.10

05

H.01.21 Engineer

Flow temperature increase during domestic hot water operation too fast

Full guide for H.01.21

06

H.00.42 Engineer

Pressure sensor open/faulty

Full guide for H.00.42

Call a Gas Safe engineer if…

You can smell gas or see signs of a leak
The Baxi shows an Emergency or High severity code
The boiler keeps locking out after repeated resets
You've tried the DIY checks and the fault hasn't cleared
There's visible water leaking from the boiler
The flame is yellow or orange instead of blue

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See the full 65-code list for the Baxi 424 COMBI 2.1