BoilerFaultCodes A7
DHW temperature sensor faulty.
Worcester Bosch Greenstar 28 Fault codes & diagnostics
18 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.
Combi Natural Gas 2012-2015 Discontinued
GC Number 47-406-33
Download the Worcester Bosch Greenstar 28 manual
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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. 18 Unrated
Just want the most common Worcester Bosch Greenstar 28 faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes
All 18 documented codes
Tap any card for details
A8
Communication fault.
Ad
Cylinder temperature sensor not detected.
b1
Code plug not detected.
b2
Internal data error.
b3
C6
Fan not running.
CC
Outside temperature sensor not detected.
d3
External limiter has tripped.
d5
External primary NTC on low loss header defect.
E2
Temperature sensor in CH flow faulty.
E9
Heat exchanger temperature limiter or flue gas temperature limiter has tripped.
EA
Flame not detected.
F0
Internal fault.
F1
Internal data error.
F7
A flame is detected although the appliance is switched off.
FA
A flame is detected after the gas has been switched off.
Fd
Reset was pressed in error.