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221834B
Has boiler been
operating for 10
seconds yet ?
Does gas ignite ?
2
YES
NO
YES
Isolate supply
NO
Replace PCB
Examine electrode and
leads. Repair/replace
as necessary
Reconnect supply
Is APS neon lit ?
Is fan running ?
Replace APS
1
Is there 240V at the fan ?
Replace ignition
PCB
Flue hood overheating-
blocked secondary heat
exchanger (clean/replace)
Replace flue hood
thermostat
Will flue hood
thermostat reset?
- is there 240V at
the fan?
Is there 240V
at C ?
YES
YES
NO
NO
YES
NO
NO
Replace fan
Switch High/Low Switch
to 'low'
Is there a spark at
electrode ?
Can the “low” gas
pressure be set
(see data tables)
at test point on gas
valve?
YES
NO
YES
Diagram 13.1
NO
Check continuity of
both main coils
Coils ok?
Replace
ignition
PCB
Replace as
necessary
YES
NO
YES
NO
YES
NO
NO
Does gas
ignite?
Faulty injector
Replace
NO
3
YES
Does discharge tube on
ignition PCB flash ?
PM5
13 Fault Finding