
Supplied By www.heating spares.co Tel. 0161 620 6677
31
221473B
3 Fault Finding
Diagram 3.5
Remove the outer case, control housing and it's cover.
Check all connections on the control board and the boiler components, rectify or renew
as necessary. Two dummy two way connectors are provided for ease of testing
continuity. Remove fuses and test for continuity, if faulty, check cables and connections
for shorting to E or N, rectify if necessary and replace fuse, with spare provided.
Check central heating water pressure, repressurize if necessary.
Make sure boiler is cold. Check all pipes and connections between the Air Pressure
Switch (APS) fan and combustion sample point. Make sure sample point cap is fitted
correctly. The boiler will go to lockout if the boiler overheat cut off goes open circuit,
or the boiler fails to detect flame.
Isolate supply, disconnect cables, is there
continuity, across boiler overheat cut off, brown and
black on APS, DHW cut out, and yellow and grey
on W.P.S. Is there 8k
Ω
-10K
Ω
across CH and DHW
thermistor ?
Replace faulty
device.
Disconnect red cables to
flow switch, turn on hot
water tap. Is there
continuity between red
cables ?
Replace faulty
flow switch.
Replace faulty
flow switch.
Is there
230V ac at
pump ?
Replace faulty
main PCB .
faulty pump
rectify.
Turn off hot water tap
is there open circuit,
between red flow switch
cables ?
Connect all cables
restore supply, does pump
run for
≈
30 seconds.
Turn on hot water tap,
is red lockout neon lit.
Carry out the initial fault finding checks described in Section 3.1.
Check that gas, water and electricity are available at the boiler.
Before starting tests isolate the boiler, make sure that the remote controls are not
calling for duty and there is no domestic hot water demand.
YES
YES
YES
YES
YES
YES
NO
NO
NO
NO
NO
NO
A
B
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