Unit installation

28
10.0Fault Finding
Check solenoid
leads for continuity
Replace P.C.B.
Does
“Boiler On”
neon light ?
Is
resistance
across sensor correct ?
(1M OHM @ 25
o
C)
Are
potentiometer
resistances correct ?
(see table on
page 26)
Check gas pressure
at inlet to valve
(20mb)
Check main injector
for blockage/damage
Is
there mains
voltage at main
solenoid ?
Is
burner setting
pressure correct ?
Disconnect orange + blue
leads & check resistance
across main gas solenoid
(approx 5K OHM)
Replace wiring
harness
Replace V404A
solenoid
Check gas valve is
operating correctly
Replace
potentiometer
Replace sensor
Replace P.C.B.
Check pump for
circulation
Check sensor is
located correctly
in pocket
Boiler unit
satisfactory
YES
YES
YES
YES
YES
YES
YES
NO
NO
NO
NO
NO
NO
NO
Replace P.C.B.
NO
Does
main burner
ignite ?
With
thermostat on
high, does boiler switch off
at approx. 82
o
C on
flow ?
Does
the boiler
operate and then
lockout ?
Check flue pull
and ventilation
Check boiler sensor
and potentiometer
Check valve
solenoids
NO
YES
YES
YES