Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Remove low voltage connector from fan

Measurement:

Check for continuity (zero resistance) of each of the
3 wires running between X3 and the disconnected plug.
Black = X3 Pin 3
Yellow = X3 Pin 4
Pink = X3 Pin 5.
Inspect harness and connectors for good overall condition.
Note:
Wires may be multicoloured.