Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Disconnect connector HV2 from the PCB

Measurement:

Test 1:
Measure the resistance between the fan neutral (blue wire / pin 3)
on HV2 and each fan connector (pins 4 to 7) on HV2 in turn.
Expect greater than 1M Ohm on each test.
Test 2:
Measure the resistance between each fan connector
(pins 4 to 7) on HV2 and a suitable earth point.
Expect greater than 1M Ohm on each test.
Test 3:
Measure the resistance between the fan neutral
(blue wire / pin 3) on HV2 to a suitable earth point.
Expect greater than 1M Ohm.