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34
Does the fan run at
all before the fault
occurs?
Does this fault only
occur in CH or DHW
mode?
Turn off boiler. Remove
multiway connector
from board position
ST16. Is there
continuity across the
green wires?
Remove fan connector
from board position
ST1
and restart boiler
in the fault mode.
After 5 seconds is
there mains 230V
from the left
(N)
track
at
ST1
and right
(L)
track if DHW mode?
Centre
(L)
track if CH
mode?
Is there continuity
across the black
wires?
Replace multiway
connector. Remove
the fan connector
from board position
ST1 and restart the
boiler in DHW mode.
After 5 seconds is
there mains 230V
across the centre (L)
and left (N) tracks at
ST1? Note: Take care
not to short L to N
Repair or replace fan
(Section 15.4.15) or
cable.
Repair or replace fan
(Section 15.4.15) or
cable.
Air pressure switch
is shorting.
Replace switch.
(Section 15.4.25)
Check black wires and
in-line connector.
FAIL POINT J “Air or W
a
ter Pr
essur
e F
ault”
No
Yes
No
No
Replace control board
(Section 15.4.11)
No
Replace control board.
(Section 15.4.11).
No
Yes
Yes
Yes
Yes
No
Yes
Does the burner ignite
(burner light on)
before fault occurs?
Pressure switch has
opened during
operation.
Check flue for
blockage.
Also investigate sense
tubes and pressure
switch.
Gain access to and
remove electrical
connectors from
pressure switch and
restart boiler. Is there
continuity between
C
and
NO
terminal
(where green wires
were fitted) when the
fan runs? CAUTION:
LIVE TERMINALS AT
THE FAN
Pressure switch has
not closed. Are the
silicon tubes in good
condition and free of
condensation.
Replace air pressure
switch (Section
15.4.25). Note: In the
unlikely event of this
not solving the
problem inspect the
pressure pick-up
(Venturi) in the fan.
Inspect the flue. Is it
free of any
restrictions?
Rectify flue problem.
Remove multiway
connector from board
position
ST16
. Is there
continuity of the
green wires?
Replace control board.
(Section (15.4.11).
Repair or replace
wires/harness/in line
connector
Replace tubes. If
condensation has
occurred, also replace
pressure switch and
check condition of
Venturi in the fan.
No
No
No
No
No
Yes
Yes
Yes
Yes
Yes