Technical data
34
Replace main PCB
Replace coil
Burner output
modulates
NO
NO
YES
YES
Check and correct:-
1. Main PCB - CM3, plug is connected to MET, i.e. Natural Gas
2. Main PCB - CM4, the RLA plug is connected to OFF
G
Volts across modulating coil and at Main
PCB - M5 connector across terminals 31, 32
Max. burner press. approx. 10 V DC
Min. burner press. approx. 1.5 V DC
Modulating coil faulty
cold resistance
approx. 40 ohm
K
Continuity across terminals 1 and 3
on reset switch when pressed
(between white wires)
Replace reset switch
Replace ignition PCB
YES
NO
YES
Check and correct:-
1. Ignition electrodes and leads
2. Electrode connections
3. Spark gap and position
H
240V at Main PCB - M8 connector,
across terminals 18, 19 and at
Ignition PCB - M1 connector,
across terminals A, C
Air pressure switch proved
neon stays off
YES
YES
Replace ignition PCB
Replace main PCB
NO
NO
neon illuminated,
Go to section ' ', page 33
E
YES
NO
Check and correct:-
1. Flame sensing electrode and lead connections
2. Electrode position
Flame current should be:-
Maximum burner pressure - 3.5 mA approx.
Minimum burner pressure - 1.5 mA approx.
I
Replace ignition PCB
Replace flame sensing electrode
J
Overheat thermostat
operated or faulty,
i.e. continuity across
thermostat terminals
Allow to cool.
Continuity across
thermostat terminals
more than 1.5 ohm
Replace overheat thermostat
Main PCB - M1 connector,
is 20V DC across terminals 49, 50
Replace neon PCB
Replace main PCB
NO
YES
YES
NO
YES
Replace main PCB
NO
YES
240V at internal clock
terminals 1 and 2
20V DC across clock
terminal 4 and Main PCB - M10
connector, terminal 30
Continuity between clock
terminal 4 and Main PCB - M13
connector, terminal 54
20V DC across Main PCB - M13
connector, terminal 54 and M10
connector, terminal 30
L
240V at Main PCB - M3 connector,
terminals 22 and 23
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
NO
YES
NO
NO
YES
Alpha 500E - Fault Finding