Common problems guide

The most common Worcester Bosch Bosch Greenstar ZWBR 7-25A problems

The faults most likely to send a Worcester Bosch Bosch Greenstar ZWBR 7-25A 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.
15 documented codes
6 most common
0 DIY-safe checks
6 engineer needed

The 6 most common faults

01
A5 Engineer

Circuit break or short circuit in the constant hot water temperature sensor.

Full guide for A5
03
AC Engineer

No electrical connection between the controller (TA211E) and the control board.

Full guide for AC
05
C1 Engineer

Air pressure switch contacts open when appliance is operating or fan speed to slow.

Full guide for C1

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 15-code list for the Worcester Bosch Bosch Greenstar ZWBR 7-25A

Related guides

Boiler losing pressure → No hot water → When to replace → Symptom checker →