Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Remove the connector from the flow turbine

Measurement:

Measure the resistance of each of the wires on the flow turbine harness as per the table below:
Flow turbine connectorConnector X3
Black Pin 13
Red Pin 2
BluePin 1

Expect continuity / zero resistance on each test.
Also visually inspect the condition of the harness and its connectors.