Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Gain access to back of display PCB
Disconnect X1 (ribbon cable) from main PCB
(this affects resistances and must be done to prevent misdiagnosis)

Measurement:

Test 1:
Set CH temperature control to maximum
Measure the resistance between connections 1 and 3 on the display PCB.
Resistance should be less than 10Ω.
Measure the resistance between connections 2 and 3 on the display PCB.
Resistance should be approximately 3kΩ.
Test 2:
Set CH temperature control to minimum.
Measure the resistance between connections 1 and 3 on the display PCB.
Resistance should be approximately 3kΩ.
Measure the resistance between connections 2 and 3 on the display PCB.
Resistance should be less than 10Ω.