Common problems guide

The most common Worcester Bosch 9/14 - 19/24 CBi problems

The faults most likely to send a Worcester Bosch 9/14 - 19/24 CBi into lockout — with plain-English causes, what to check first, estimated repair costs and whether you need a Gas Safe engineer.

This model is discontinued. Parts can be harder to source and expensive. If repair costs are mounting, a new A-rated boiler may be the smarter choice.

The 6 most common faults

01

A High Engineer

Your boiler has lost all power and is completely unresponsive, meaning it is currently unable to provide heating or hot water.

Est. cost: £120-250
Parts: Printed Circuit Board (PCB), Internal Fuse, Power Cable

Full guide for A

02

B High Engineer

Your boiler is receiving a signal to turn on but is failing to start the ignition process, suggesting a communication or sensor delay.

Est. cost: £120-250
Parts: Printed Circuit Board, Flow switch, Ignition lead

Full guide for B

03

C High Engineer

Your boiler is failing to ignite or stay lit, meaning it cannot produce heat or hot water because the flame is not being detected.

Est. cost: £120-250
Parts: Ignition electrode, Flame rectification probe, Gas valve

Full guide for C

04

D High Engineer

Your boiler has stopped working for safety reasons and is locked out, meaning it needs a manual reset or a professional technician to investigate the internal fault.

Est. cost: £120-250
Parts: Ignition electrode, Gas valve, PCB

Full guide for D

05

E High Engineer

Your boiler has stopped working for safety reasons and is waiting for you to manually reset it to try and clear the fault.

Est. cost: £120-250
Parts: Ignition electrode, Gas valve, Printed Circuit Board (PCB)

Full guide for E

06

F High Engineer

Your boiler has detected an unspecified internal problem and has shut down as a safety precaution.

Parts: Main control board, Wiring harness, Internal sensors

Full guide for F

Parts most often replaced

on the Worcester Bosch 9/14 - 19/24 CBi

Printed Circuit Board (PCB)Internal FusePower CablePrinted Circuit BoardFlow switchIgnition lead

Based on parts cited in our fault code database. Your engineer will confirm what's actually needed after diagnosis.

Call a Gas Safe engineer if…

You can smell gas or see signs of a leak
The Worcester Bosch 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

See the full 6-code list for the Worcester Bosch 9/14 - 19/24 CBi