Worcester 26CDi XTRA Installation And Servicing Instructions page 43

No
Is the gas supply
connected and at the
correct pressure?
Yes
Remove front panel.
No
Reset and restart the
boiler. Can a flame be
seen through the spy
glass?
Yes
Turn off boiler. Remove
inner cover and
combustion chamber
cover. Is the sense
electrode and lead in
No
good condition and is
gap correct.
Yes
Remove multiway
connector from board
No
position ST16.
Is there continuity
from contact 11 (white
wire) to flame sensor?
Yes
No
Does the flashing fault
signal occur at the
start of a demand?
Yes
Replace control board (Section 14.3.23).
Note: It is not possible to reliably check
the cross-light performance of the burner.
In the unlikely event of such a fault,
investigate flue problems or replace
burner or injector. (Section 14.3.7/8).
Rectify gas supply
problem.
Remove inner cover.
No
Reset and restart the
boiler. Does a spark
occur across the
electrodes?
Yes
Turn off boiler. Remove
the multiway
connector from board
position ST16. Test
No
resistance across
contacts 7 and 8
(brown wires) and 9
and 10 (violet wires).
Are both readins
below 100 ohms?
Yes
Replace control board.
(Section 14.3.23)
Repair or replace flame
sensor
(Section 14.3.10)
or wiring.
Flashing occurs at end
of demand. Replace
gas valve.
(Section 14.3.11).
43
No
Are the electrodes and
gap and connections
in good order?
Yes
Replace control board.
(Section 14.3.23).
Remove both brown
connectors from gas
valve.
No
(First remove pressure
switch bracket).
Is there continuity
from the brown and
violet wires to
multiway connector?
Yes
Replace gas valve.
(Section 14.3.11)
Repair or replace
electrodes
(Section 14.3.9)
or HT leads
Repair or replace
harness.