15
Symptom Possible Cause Remedy
ST9400S has a blank
LCD display
No power to the
heating system
Check that there is power to the
heating system
Fault in ST9400S Call Installer
ST9400S indicates
that Heating and/or
Hot Water are ON, but
radiators are cold and/
or taps are running
with cold water.
Temperature controls
are switched off or
set too low
Check that the temperature controls
in the system are set to appropriate
levels
Boiler or other
system controls
have malfunctioned
Call Installer
ST9400S shows the
message:
‘INTERNAL FAULT’
Fault in ST9400S Call Installer
Every few seconds,
the ST9400S screen
shows the message:
ST9400S is
counting down the
number of days
until your next boiler
service is due.
Arrange a boiler service before the
counter reaches zero.
After servicing your boiler, the Service
Engineer / Installer will reset the
ST9400S to remind you when the next
boiler service is due. Each service is
normally a maximum of 1 year apart.
Although the heating
is still operating, the
ST9400S screen keeps
flashing the message:
Your boiler service
is OVERDUE.
Arrange an immediate boiler service.
After servicing your boiler, the Service
Engineer / Installer will reset the
ST9400S to remind you when the next
boiler service is due. Each service is
normally a maximum of 1 year apart.
The ST9400S screen
shows the message:
Your boiler service
is OVERDUE and
the boiler has
been automatically
switched off to
ensure your safety.
Arrange an immediate boiler service.
If set to do so, it may be possible to
obtain limited use of the boiler by
pressing any EXTRA HOUR button.
Each button press will allow operation
of the boiler for 1 hour at a time, and
the screen will display the message
“On 1h”.
After servicing your boiler, the Service
Engineer / Installer will reset the
ST9400S to remind you when the next
boiler service is due. Each service is
normally a maximum of 1 year apart.
Troubleshooting Guide
This is a quick guide to help you diagnose and cope with possible problems with
ST9400S. For further assistance, please contact your Installer.
FAQ AND TROUBLESHOOTING
