Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Disconnect mains voltage plug from fan
Pull X1 back slightly to expose test pins

Measurement:

Measure the resistance of the blue and red wires running from the disconnected plug to X1 on the PCB.
Red = X1 Pin 1
Blue = X1 Pin 2.
Inspect harness and connectors for good overall condition.