Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance

Measurement:

Test 1. Measure for resistance across pins 4 (Brown) and pin 5 (Blue) of X3 connector.
Expected resistance Greater than 1 MOhm.
Test 2. Measure for resistance across pin 4 (Brown) and Earth
(Main terminal block).
Expected resistance Open Circuit.
Test 3. Measure for resistance across pin 5 (Blue) and Earth
(Main terminal block).
Expected resistance Open Circuit.