Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Remove the main PCB to gain access to the display PCB

Measurement:

Measure the resistance across the center and right pins of the selector switch potentiometer (located on the display PCB).
The resistances measured will alter as potentiometer is turned and should conform (approximately) with the readings below.
Setting
Resistance (Ω)
Off
4.2k - 5k
On
2.4k - 2.9k
Reset
0 - 500

Note:
Ensure a good connection is made.