Set Appliance State:

Mains Power Off
Set Multimeter to AC Voltage Set meter to measure AC Volts
CH Demand
Mode Switch in LOW position
WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure
Mains Power On

Measurement:

Allow the Fan to start and the Pilot to ignite.
Measure the Voltage across the Black wire (connection marked ML) and the Blue wire (connection marked MN) on PCB connector PL3.