Worcester 28Si Installation And Servicing Instructions page 33

No
Is the facia on/off
switch turned on?
`(Clockwise)
Yes
Is there a 230V AC live
No
supply across
Terminal ST12 pins L
and N
Yes
No
Has fuse F1 blown?
Yes
Replace fuse and investigate cause. Suggestions: Cable
damage, connections to (or faults within) pump, fan,
external 230V controls, transformer or board.
No
Has fuse F2 blown?
Yes
Replace fuse.
This will be caused by
fuse fatigue or by the
board.
Green diode is damaged.
Replace control board.
(Section 15.4.10)
Turn switch on.
Check electrical
supply to boiler.
Replace control board
(Section 15.4.10)
Remove control board from facia
(See Section 15.4.10) and sepa-
rate transformer from board.
Measure resistance across the
two pairs of adjacent pins on the
transformer. Are any pair above
100 ohms?
Yes
Replace transformer.
33
Replace
No
control
board
(Section
15.4.10).