Set Appliance State:

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

Measurement:

Test 1:
Measure the resistance between the 2 purple wires.
Expected resistance approximately 45 Ohms.
Test 2:
Measure resistance between each purple wire to a suitable earth point.
Expected resistance greater than 1 MOhm.