Set Appliance State:

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

Measurement:

Measure the voltage between pin 9 (Blue) and pin 8 (Black) at connector X8 on the PCB.
Voltage may fluctuate but should be approximately 2.5V DC.
Notes:
Wires may be multicoloured.