Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Remove the 3 wire connector from the fan
Remove connector X4 from the PCB

Measurement:

Check for continuity (zero resistance) between the two wires running from pins 1 and 2 at X4 to the corresponding wire at the 3 wire fan connector.
Also visually inspect the condition of the harness and its connectors.