Alpha CD25X - 10.4 Fault Finding Solutions A-D

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Alpha CD25X/28X - Fault Finding
10.4 FAULT FINDING SOLUTIONS A to D
NO
YES
Pump
If pump jammed, release
Replace PCB
NO
PCB - X3 connector, terminals 2, 3
B
Replace pump
1.
2.
240 V ac at:-
Replace PCB
Replace PCB
Replace PCB
Replace transformer
NO
NO
NO
NO
YES
NO
NO
NO
Main terminals L and N
Check electrical supply
Replace fuse
Check wiring
Main terminal fuse
PCB - X12 connector, terminals 5, N
Neon D
illuminated continuously
A
240 V ac at:-
1.
2.
3.
NO
YES
Replace fuse
Neon D illuminated contiuously
Is 240 V ac across
PCB X6 connector terminals 1, 2
Is 26 V ac across
PCB X4 connector terminals 1, 2
PCB fuse
4.
C
DHW/Primary temp. sensor faulty. Cold resistance approx.
12-14 k ohms (resistance reduces with increase in temp.
i.e. when hot, resistance is approximately 3 k ohms)
Check and correct connections/wiring at sensor and PCB
2.
1.
YES
YES
Check resistance throughout
the range from cold to hot
DHW temperature sensor faulty
i.e. heating OK. Hot water operates
but does not modulate
Primary temperature sensor faulty
i.e. no heating or hot water
Replace sensor
Boiler cycles on and off
Remove the motor from the diverter valve.
Does the piston move in and out when
operating the boiler between CH and DHW
In CH mode. PCB - X15 connector, is 240 V across terminals 4, 6
In DHW mode. PCB - X15 connector, is 240 V across terminals 4, 5
YES
YES
NO
Replace lead
Check continuity of plug and lead
NO
NO
NO
YES
YES
Is diverter valve spindle sticking
D
Check and correct:-
1. Electrical connections
2. Restriction in flue
Neon A and B flashing
at the same time
YES
YES
(BUT)
1.
Replace PCB
Ensure by-pass slot is in horizontal position
and that the valve is not stuck open
Replace diverter valve
Replace PCB
Replace PCB
Replace motor
YES
NO
NO
2.
3.
3.
Fan connections correct at fan and PCB connector X13
Fan runs at maximum speed
PCB connector, is 36 V dc across terminals 5 and 3 or 4
Fan jammed or faulty winding
Is dc volts at PCB, X13 connector:-
across terminals 5 and 4 - 34 V dc
across terminals 2 and 4 - 4 V dc
YES
YES
YES
Replace fan
Replace fan