Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to Resistance 
Remove connector X9 from the PCB
Remove connector from DHW thermistor
Remove connector from DHW thermistor
Measurement:
Measure the resistance across each of the wires of the DHW thermistor harness between pins 3, 4 (white leads) X9 connector and the DHW thermistor connector.
Expect continuity / zero resistance on each wire.
Expect continuity / zero resistance on each wire.
Isolate as per TOPs P4
and refit as necessary