Technical data

11.0 Fault Finding
42
START
Replace fan
Replace harness
Replace pressure
switch
Replace fan
Replace
thermostat
Does fan run ?
Is
there a clear
constant spark at
the electrode ?
Change
potentiometer
Is
there mains voltage
at S/L input ?
Is
there mains voltage
at Pump L output ?
Check fuse on
circuit board
Check pump wiring
Note: This can occur if
the boiler has
overheated
Reset by turning
control knob OFF, wait
10 seconds then turn
ON
Does
lockout light
go out ?
Is
"Fan On"
light on ?
Check control knob
is turned on
Check that the wires
are connected to the
thermostat sensor
Check that the fan &
pressure switch plug is
connected
Is there
continuity between
C & NC terminals
on the pressure
switch ?
Check pressure switch
pipes for leaking or
blockage
Note: Under cold
conditions fan run up
time may exceed
1 min
Ensure external
controls are calling
for heat
Does pump run ?
Is
"Pilot On"
light on ?
Is
lockout light
on ?
Is
"Boiler On"
light on ?
Is
there mains voltage
at P/L input ?
Is
there mains at
the fan
connection ?
Is there
continuity across
the overheat
thermostat ?
YES
NO
YES
YES
YES
YES
YES
NO
YES
YES
NO
NO
NO
NO
NO
YES
YES
YES
NO
NO
NO
NO
YES
NO
No continuity - change
sensor
Check continuity
across pilot solenoid
(1.5 K OHM)
No continuity - change
pilot solenoid
Check continuity
across sensor
(1 M OHM at 20
o
C)
Investigate
pump
Change PCB
No continuity
across fuse,
change fuse
YES
YES
Change PCB
Check & clean
electrode. Check gap &
lead
YES
Check external
wiring
NO
Check Potentiometer
(see table)
Before starting FAULT FINDING carry out
preliminary electrical system checks i.e.
Earth Continuity, Polarity, Short Circuit
and Resistance to Earth.