41
14.0 FAULT FINDING
Publication No. 5106451
Reset lockout,
does fan run ?
Check for short
circuits on ignition
PCB and gas valve
if OK replace fuse.
Is
there no spark and
no gas (check at
meter) ?
Incorrect gas
supply to boiler.
Is there spark
but no gas ?
Does
control PCB fan
connection have
12 Vac across it
(L)
?
Replace fan.
Is there
230V at control
PCB connection to
ignition PCB
(M)
?
Is
18.1mbar
dynamic at gas
valve inlet ?
Is
spark probe
damaged ?
Replace spark probe.
Is
there 230V
at ignition PCB
connection to control
PCB
(N)
?
Replace ignition PCB.
Replace ignition
PCB.
Is
wiring from ignition
PCB to spark probe
OK ?
Rectify wiring.
Ignition Lockout
YES
Is
there gas but
no spark ?
Wiring from control
PCB to fan faulty.
NO
YES
NO
NO
Does
fan
connection have
12 Vac across it
(K)
?
Replace control PCB.
Is ignition PCB
fuse OK ?
Replace control PCB.
Wiring from control PCB
to ignition PCB faulty.
Is
spark gap
between 3 and
5mm ?
Set spark gap to 4mm.
Is there
230V at ignition PCB
connection to gas
valve
(O)
?
Is there
230Vdc at the end of
the gas valve lead ?
(P)
Is
sensing tube
blocked ?
Unblock tube.
Replace ignition PCB.
Replace gas
valve lead.
Replace gas
valve.
Is the detection
probe damaged ?
Is
wiring from ignition
PCB to detection
probe OK ?
Is there
230V, ignition PCB
burner on pin to
control PCB
(Q)
?
Replace control
PCB.
Replace detection
probe.
Rectify wiring.
Replace ignition PCB.
Burner on, wiring from
ignition PCB to control
PCB faulty.
Is there
230V control PCB
burner on pin to
ignition PCB ?
(R)
NO
YES
YES
NO
NO
YES
YES
YES
YES
NO
NO
NO
YES
YES
NO
YES
NO
NO
YES
YES
YES
YES
YES
NO
NO
NO
YES
NO
YES
YES
NO
YES
YES
NO
NO
Spark
Electrode
Ignition
PCB
Control
PCB
Condensate
Trap
Detection Electrode
Gas
Valve
Mains
Input
Optional
Pump Feed
Transformer
Overheat Stat
Casing
Stat
Thermistor
Dry Fire
Flow Switch
DC
Fan
On/Off
Switch
br
r
br
w
g/y
g/y
br
b
b
b
b
b bk
br
br
bk
bk
bk
bk
bk
r
r
r
br
g
w
N P/F
bk
S/L
v
w
g/y
O
N
M
L
K
Fan Connection
when unplugged
P
R
Q