Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Gain access to PCB
Disconnect connector X23 from the PCB

Measurement:

Measure the resistances between the
4 wires to the fan (pins 3 to 6 on X23).
Resistances should conform approximately to the table below.