
Supplied By www.heating spares.co Tel. 0161 620 6677
35
221474C
Switch off CH
demand.Switch
on DHW.
Does boiler go into
ignition sequence?
Is the Vdc on CN4
pins 8/9 greater
than 10 Volts
YES
Faulty DHW
thermistor.
Faulty
flow
sensor.
Does boiler
go to lockout?
Faulty
DHW
stat.
Faulty
main
PCB.
Has CH
overheat gone
open circuit?
Faulty
main
PCB.
Faulty
main
PCB.
Faulty sense
electrode.
Faulty CH
thermistor.
Is CH thermistor
resistance correct
10k ohms cold
1.6k ohms hot?
Check pump
spindle is free.
Turn to
release.
Replace
pump.
Correct
operation.
NO
NO
NO
NO
NO
YES
NO
YES
YES
NO
YES
YES
Is DHW thermistor
10k ohms cold?
YES
YES
Is there continuity
of boiler protection
thermostat?
NO
Is there 230Vac
on CN2-B pin
7+8 to pump?
NO
YES
3 Fault Finding
Diagram 3.5
6419