Set Appliance State:

Set Multimeter to Resistance Set meter to measure resistance
Isolate Mains Power to appliance as per TOPs P4
Selector Switch OFF

Measurement:

Unplug connector CN4 from the Main Control PCB.
Check for open circuit resistance across the Selector Switch (both Brown wires on the unplugged connector CN4).
Selector Switch On.
Check for short circuit resistance across the Selector Switch (both Brown wires on the unplugged connector CN4).
Replace connector CN4 on the Main Control PCB.