Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to Resistance 
Remove the wires from the selector switch noting their locations
Selector switch in Winter mode
Selector switch in Winter mode
Measurement:
Measure the resistance between the terminals C and 3.
Resistance should be short circuit (zero resistance).
Is the resistance measured as expected?
Resistance should be short circuit (zero resistance).
Is the resistance measured as expected?
Isolate as per TOPs P4
and refit as necessary