Worcester 25Si Installation And Servicing Instructions page 34

With CH control knob
fully clockwise, does
No
the boiler ignite and
appear to run
normally in central
heating mode?
Yes
Red diode is
damaged. Replace
control board.
(Section 15.4.10)
With a hot water tap
fully open, does the
No
boiler ignite and
appear to run
normally in hot water
mode?
Yes
Red diode is
damaged. Replace
control board.
(Section 15.4.10)
No
Is there 230V AC
across terminal ST8
pins LR and N?
Yes
No
Is there a link at
terminal ST13 pins 1
and 2?
Yes
Is there an electronic
No
programmer at
position ST5 at right-
hand end of board?
Yes
Remove programmer
No
connector from board
edge. Does CH lamp
now light?
Yes
Correctly set or
replace electronic
programmer.
Remove multiway
connector from board
No
position ST16. With
tap still open is there
continuity across
contacts 19 and 20
(2 pink wires)?
Yes
Replace control board.
(Section 15.4.10).
34
There is no heat
demand. Check room
thermostat or mains
programmer (or link).
Insert a link
Replace control board.
(Section 15.4.10).
Locate and observe the
flowswitch assembly
(behind the air pressure
switch). Does the lever
No
above the microswitch
move up and down with
the demands, thus
activating and
de-activating the
microswitch?
Yes
Check or replace
wiring or microswitch
Replace flowswitch
assembly