Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to Resistance 
Disconnect flow switch plug at the PCB
Disconnect the flow switch at the inline connector
Disconnect the flow switch at the inline connector
Measurement:
Check for continuity (zero resistance) between each end of the two wires to the flow switch.
Inspect harness and connectors for good overall condition.
Inspect harness and connectors for good overall condition.
Isolate as per TOPs P4
and refit as necessary