Set Appliance State:

Set Multimeter to Resistance Set meter to measure resistance
Isolate Mains Power to appliance as per TOPs P4

Measurement:

Measure the resistance between connection 3 (White wire) on CON2 on the Fan Driver PCB and the Metal Fan Laminations on the Fan body. Repeat this measurement using connection 4 (Grey wire) and again using connection 8 (Purple wire) on connector CON2 on the Fan Driver PCB instead of connection 3 (White wire). An Open Circuit reading should be obtained for each measurement.