Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Disconnect connector X4 at the PCB

Measurement:

Measure the resistance between pins 1 and 2 (black wires) at the disconnected connector.
Resistance should be short circuit.
Note:
Remember if a white PCB is fitted
X4 is in a different position.