Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Remove the harness from J10 of the main PCB
Undo the 4 screws and remove the display PCB from the
control panel leaving the harness attached
Place the plug from J10 conveniently near the reset switch on the board

Measurement:

Test 1:
Measure resistance across the left hand pin of the switch and the 3rd pin
on the lower set of connections of the plug removed from J10.

Test 2:

Measure resistance across the right hand pin of the switch and the 4th pin
on the lower set of connections of the plug removed from J10.