Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to DC Volts Set meter to measure DC Volts
Gain access to PCB
Use insulation mat as required
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

With the fan running measure the DC voltage between the yellow wire (pin 5) at connector J4 on the PCB and a suitable earth point.
Expect approx. 12V DC.