37
Is the boiler fully
water pressurised and
is all air vented?
Rectify fault.
No
No
Reset and restart the
boiler in CH mode.
Does the pump run?
Yes
Remove front panel.
Reset and restart the
boiler. Can a flame be
seen through the spy
glass?
Remove inner cover.
Reset and restart the
boiler. Does a spark
occur across the
electrodes?
Turn off boiler. Remove
the multiway
connector from board
position
ST16
.
Test resistance across
connector contact
pins
1
and
2
(green wires)
and
8
and
9
(brown wires).
Are both reading
below 100 ohms?
Replace gas valve.
Are the electrodes and
gap and connections
in good order?
Replace
control board.
Remove both
connectors from gas
valve.
Is there continuity
from these
to multiway
connector?
Repair or replace
harness.
Repair or replace
spark electrode
or HT leads
Is the gas supply
connected and at the
correct pressure?
Rectify gas supply
problem.
No
No
No
No
No
No
Yes
Yes
Yes
Yes
Yes
Yes
Replace control board.
If problem not solved
replace gas valve.
Yes
Replace or repair
pump.
Yes
TEST D
Test resistance of each
ignition cable.
Is it 2000-3000 ohms?
Yes
No
Replace (both) ignition
cables
Is there continuity
between pins 6 and 7?
(green wires to HL
stat)
Replace overheat stat
or wiring to it.
No