Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to Resistance 
Remove the white wire from the primary flow overheat thermostat
Disconnect the in-line connector joining the white and blue wires
Disconnect the in-line connector joining the white and blue wires
Measurement:
Measure the resistance between the two disconnected white wires.
Expect continuity / zero resistance.
Is the resistance measured as expected?
Expect continuity / zero resistance.
Is the resistance measured as expected?
Isolate as per TOPs P4
and refit as necessary