BoilerFaultCodes A5
Circuit break or short circuit in the constant hot water temperature sensor.
Worcester Bosch Bosch Greenstar ZWBR 7-25A Fault codes & diagnostics
15 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.
Combi Natural Gas 1999-2001 Discontinued
GC Number 47-311-44
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The fault code is already on your display
Note it down before pressing reset — resetting clears the code immediately. How to read fault codes →
Severity at a glance
Each cell = one fault code. Hover to identify. 15 Unrated
Just want the most common Worcester Bosch Bosch Greenstar ZWBR 7-25A faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes
All 15 documented codes
Tap any card for details
A7
Circuit break or short circuit in the dhw temperature sensor.
AC
No electrical connection between the controller (TA211E) and the control board.
b1
Code plug.
C1
Air pressure switch contacts open when appliance is operating or fan speed to slow.
C4
Air pressure switch contacts do not open.
C6
Air pressure switch contacts remain open.
CC
Circuit break between outside temperature sensor and control unit.
d3
E0
Internal fault on control board.
E2
Circuit break or short circuit on ch temperature sensor.
E9
Safety temperature limiter has tripped
EA
No ionisation (flame sense) current.
F7
Incorrect ionisation (flame sense) signal.
FA
Ionisation (flame sense) current remains after normal shut down i.e burner does not go off.