Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to Resistance 
Remove connector X20 from the PCB
Measurement:
Measure the resistance across pins 3 & 4 of connector X20.
Resistance varies with temperature and should conform approximately to the graph below:
Resistance varies with temperature and should conform approximately to the graph below:
Isolate as per TOPs P4
and refit as necessary