Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Remove connector CN3 from the PCB

Measurement:

Test 1.
Measure for resistance across pins blue and brown of connector CN3.
Expected resistance greater than 1Mohm.
Test 2.
Measure for resistance across brown and a suitable earth connection.
Expected resistance greater than 1Mohm.