Set Appliance State:

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

Observation:

With the gas control valve knob depressed, measure the voltage across connection 40 on Fan Resistor (bottom side of resistor) and a suitable earth point.
Note:
Connections to resistor may vary depending on appliance age.