
Supplied By www.heating spares.co Tel. 0161 620 6677
34
221474C
YES
NO
Apply CH
demand.
Is there
continuity across
yellow & black
on WPS?
Faulty water
pressure switch.
Replace
Replace
CVI box.
Is ignition
burner pressure
at least 2.0 mb?
Does red
lockout light?
Reset lockout
switch.
Is there a spark
at electrode?
NO
YES
YES
Is TXR
supply 230Vac?
NO
Is there
at least 30Vac on
TXR secondary?
YES
NO
NO
Is there 230Vac
CN2B pins 5 & 6
on main PCB?
NO
Faulty
CVI
Does burner
pressure increase
after ignition?
YES
NO
YES
Do sparks stop
after burner is lit?
Does boiler
go to lockout?
Faulty sense
electrode
Correct CH
operation
Is there
30Vac CN7 on
pins 3 & 4 and
0.8Vdc on pin 1
& 2 CN7?
Faulty
main
PCB
Isolate supply. Is the
resistance at CN2 on
the fan driver PCB
between White and
Grey, Grey and Purple,
Purple and White
approx 2.5ohms ?
Is there continuity at
CN2 on the fan driver
PCB between White
and the fan motor
laminations? (repeat
with Grey and Purple).
NO
Faulty fan.
Replace.
Faulty fan.
Replace.
Faulty fan driver
PCB. Replace.
NO
YES
NO
YES
NO
NO
NO
Faulty
CVI
YES
NO
YES
YES
YES
YES
YES
Faulty
TXR
Faulty
main
PCB
NO
start
Is there 300Vdc
DC power out of
pins on CVI box
to gas valve?
Check continuity
on valve.If faulty
replace.
Does fan run
at ignition rate?
3 Fault Finding
Diagram 3.5
6418