Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Disconnect the Fan Connector from the PCB
Disconnect the Fan Connector from the Fan Assembly

Measurement:

Measure the resistance (continuity) across each of the 5 wires in the fan harness.
Expect continuity/zero resistance across each wire in the harness.
Also check the condition of the harness visually.