Technical data

33
10.4 FAULT FINDING SOLUTION SECTIONS A to L
Main PCB - M11 connector,
is 2V DC across terminals
46, 49
Replace main PCB
Replace neon PCB
NO
NO
YES
NO
NO
NO
NO
Main terminals L and N
Check electrical supply
Replace fuse
Replace suppressor
Check wiring
Main terminal fuse
Both sides of suppressor
PCB - M4 connector, terminals 10, 11
neon
illuminated
A
240 V at:-
1.
2.
3.
4.
E
NO
NO
Main PCB - M7 connector, is
240 V across terminals 2, N
Replace air pressure switch
YES
Check and correct:-
1. Electrical and pressure tube connections
2. Blockage of pressure tubes
3. Restriction in flue
neon
stays off
Replace main PCB
D
YES
YES
NO
DHW/Primary temp. sensor faulty
Cold resistance approx. 11 k ohms
(resistance reduces with increase in temp.)
Replace sensor
1.
2.
Fan connections correct at fan and PCB
Main PCB - M7 connector,
is 240 V across terminals 4, 5
Fan jammed or
faulty winding,
i.e. cold resistance
45 ohm
YES
Replace fan
Press red reset button
240V at gas valve and across
ignition PCB - M2 connector,
terminals I, H
240V at ignition PCB across
M1 connector, terminal D and
M2 connector, terminal F
YES
YES
F
Gas at burner
Replace gas valve
NO
NO
NO
NO
Replace reset switch
Replace ignition PCB
YES
Ensure gas is on
and purged
Red reset button
illuminated
NO
YES
Pump
If pump jammed, release
Replace main PCB
NO
Main PCB - M9 connector,
terminals 20, 21
B
Replace pump
1.
2.
240 V at:-
NO
Continuity across flow switch’s microswitch
and PCB - M10 connector, terminals 28, 29
Replace microswitch
C
NO
NO
YES
YES
CH system pressure 1.0 bar
Re-pressurise system
Vent air, then replace pump
Replace differential flow switch
Is microswitch located
in correct position
NO
Pump circulating water
Differential flow switch’s diaphragm
spindle operates microswitch
1.
2.
3.
Alpha 500E - Fault Finding