30
Is the facia on/off
switch turned on?
`(Clockwise)
Is there a 230V AC live
supply across
Terminal ST12 pins L
and N
Has fuse F1 blown?
Replace fuse and investigate cause. Suggestions: Cable
damage, connections to (or faults within) pump, fan,
external 230V controls, transformer or board.
Turn switch on.
Check electrical
supply to boiler.
Replace control board
(Section 15.4.11)
FAIL POINT A
No
No
Yes
Yes
Yes
No
This could be caused
by the board or
internal
wiring/components
Has fuse F2 blown?
Replace
control
board
(Section
15.4.11).
Remove control board from facia
(See Section 15.4.12) and sepa-
rate transformer from board.
Measure resistance across the
two pairs of adjacent pins on the
transformer. Is any pair above
100 ohms?
Replace transformer.
FAIL POINT B
No No
Yes
Yes
Green diode is damaged.
Replace control board.
(Section 15.4.11)
FAIL POINT C
Red diode is
damaged. Replace
control board.
(Section 15.4.11)
Is there a link at
terminal ST13 pins 1
and 2?
Is there an electronic
programmer at
position ST5 at right-
hand end of board?
Replace control board.
(Section 15.4.11).
With CH control knob
fully clockwise, does
the boiler ignite and
appear to run
normally in central
heating mode?
Is there 230V AC
across terminal ST8
pins LR and N?
There is no heat
demand. Check room
thermostat or mains
programmer (or link).
Insert or tighten link
FAIL POINT D
No No
No
No
No
Yes
Yes
Remove programmer
connector from board
edge. Does CH lamp
now light?
Yes
Correctly set or
replace electronic
programmer.
Yes
Yes
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