Set Appliance State:
Set Multimeter to Resistance 
Isolate Mains Power to appliance as per TOPs P4
CH Mode Switch in its 24hrs position
CH Mode Switch in its 24hrs position
Measurement:
Remove the Blue spaded lead and the Yellow spaded lead from the CH Mode Switch, and measure the resistance across the exposed Switch terminals.
Reconnect leads after test.
Reconnect leads after test.
Isolate as per TOPs P4
and refit as necessary