Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to DC Volts Set meter to measure DC Volts
DHW Demand
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

With the connector attached to the pcb, measure the DC volts at the PCB connector X23 on the harness from each wire listed in the table to the neutral at incoming mains terminal strip.
Voltages should be approximately as follows;
Lead
DC Volts
Black
4.5-6
Green
0

Note: Ensure a good connection is made.