Set Appliance State:
Mains Power Off
Gas Off
Set Multimeter to Resistance 
Disconnect connector marked M1/M7 from main PCB 23
Measurement:
Test 1:
With DHW temperature selector set to Max measure the resistance across the red wire (connection 6) and the orange wire (connection 5). Resistance measured should be approximately 10 kOhms.
Turn DHW temperature selector to Min resistance should reduce to less than 100 Ohms.
Test 2:
With DHW temperature selector set at Min measure the resistance across the red wire (connection 6) and the orange wire (connection 7). Resistance measured should be approx 10 kOhms.
Turn DHW temperature selector to Max resistance should reduce to less than 100 Ohms.
Replace connector after test.
With DHW temperature selector set to Max measure the resistance across the red wire (connection 6) and the orange wire (connection 5). Resistance measured should be approximately 10 kOhms.
Turn DHW temperature selector to Min resistance should reduce to less than 100 Ohms.
Test 2:
With DHW temperature selector set at Min measure the resistance across the red wire (connection 6) and the orange wire (connection 7). Resistance measured should be approx 10 kOhms.
Turn DHW temperature selector to Max resistance should reduce to less than 100 Ohms.
Replace connector after test.
Isolate as per TOPs P4
and refit as necessary