Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Disconnect blue wire from selector switch
Disconnect brown wire in the middle of the selector switch
(this should run from the selector switch to the overheat thermostat)

Measurement:

Measure the resistance across the two exposed
terminals of the selector switch.
Short circuit (zero resistance) expected.