Set Appliance State:

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

Measurement:

Allow the Fan to start.
Measure the Voltage across the Red wire (connection marked PL) and the Blue wire (connection marked MN) on PCB connector PL3.