Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Disconnect plug ST1 from the PCB

Measurement:

Test 1:
Measure the resistance between the white and black wires on the disconnected plug.
Resistance should be approximately 102 Ohms.
Test 2:
Measure the resistance between the red and black wires on the disconnected plug.
Resistance should be approximately 46 Ohms.
Test 3:
Measure the resistance between the white wire on the disconnected plug to a suitable earth point.
Resistance should be greater than 1M Ohm.