Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to DC Volts Set meter to measure DC Volts
Remove control box cover if necessary
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Measure the DC voltage between the PCB connector X23 and the neutral on the incoming mains terminal strip for each of the wires listed in the table below, with the connector X23 attached to the PCB.
Voltages should be approximately as follows;
Lead
DC Volts
Black
4.5-5
Green
0

Note:
Ensure a good connection is made.