Set Appliance State:

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

Measurement:

Test 1:
Measure resistance across the Red
(marked 7.1) and Blue (marked 7.2) on X4.
Expect resistance of approximately 6.1k Ohms.
Test 2:
Measure resistance across the Orange (marked 7.3) and Blue (marked 7.2) on X4.
Expect resistance of approximately 900 Ohms.
Test 3:
Measure resistance between each wire -
Red (marked 7.1), Blue (marked 7.2) and Orange (marked 7.3) and a suitable earth point.
Expect resistance greater than 1M Ohm on each wire.