Alpha CD35C - Page 36

36
Alpha CD25C/28C/35C - Fault Finding
10.5 FAULT FINDING SOLUTIONS E to K
YES
Check and correct:-
1. Ignition electrode and lead
2. Electrode connections
3. Spark gap and position
4. Connections at ignition generator and PCB connector X7
5. Blocked flue
F
Is spark generator (T2)
making a clicking noise
PCB, X7 connector is 200V ac
across terminals 22, 23 during ignition
Replace PCB
Replace ignition
generator
NO
NO
YES
H
Replace pump
Allow to cool. Continuity across thermostat terminals
Replace overheat thermostat
NO
YES
Vent air, clear blockage
YES
Air in main heat exchanger, blocked heat exchanger/pipework
or pump not circulating water
NO
YES
240V at internal clock
terminals 1 and 2
I
240V at PCB - X1 connector,
terminals 55 and 2
240V at PCB - X1 connector, terminals 34 and 2
Wiring between clock
and PCB is correct
YES
YES
NO
YES
Continuity across
clock terminals 3 and 4
Internal clock calling for heat
Wiring between clock
and PCB is correct
Replace clock
Check external controls
are calling for heat
YES
YES
NO
J
Replace primary pressure switch
Replace PCB
Continuity across primary
pressure switch terminals
36 V DC at PCB across
X9 connector terminal 45
and X8 connector terminal 46
YES
NO
NO
YES
YES
YES
YES
YES
YES
Replace PCB
Replace PCB
Replace lead
Replace motor
Replace valve
Replace DHW flow switch
Continuity across DHW
flow switch (hot tap on)
Diverter valve spindle operating
Check DHW heat exchanger for blockage
Check by-pass valve is not stuck open
36 V DC at PCB across X8 connector terminals 46, 47
240 V AC at PCB across X5 connector terminals 15, 17
Remove the diverter valve motor, is the brass piston
fully extended (flush with plastic housing)
Flow rate above 2.5l/min
Check mains supply.
Clean mains inlet filter
Check continuity of
motor plug and lead
NO
NO
YES
NO
NO
NO
NO
NO
NO
K
G
Check and correct:-
1. Pressure tubes are connected and not blocked
2. If explosive ignition, check wiring to ignition generator is correct
E
Check pressure tubes are connected
PCB - X7 connector, is 240 V across terminals 26, 27
YES NO
Gas at burner
Replace gas valve
Adjust gas valve
NO
NO
Ensure gas is on and purged
Replace PCB