Set Appliance State:

Mains Power Off
Gas Off
Set Multimeter to AC Volts Set meter to measure AC Volts
Selector Switch in OFF position.
WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure
Mains Power On

Measurement:

Measure Voltage across connector M7 connection 27
(Brown wire) and connection 28 (Blue wire) on the main PCB.