Set Appliance State:

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

Measurement:

Reset ignition lockout as necessary.
Measure the AC voltage between the two fan terminals.
Expect mains voltage.
Is the voltage measured as expected?