Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Gain access to PCB (use Insulation Mat as required)
Selector Switch ON
Disconnect connector CN4

Measurement:

Measure resistance across CH Thermistor (Orange wires).
This should be in the range 2K ohms (Hot) to 13K ohms (Cold).