Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to DC Volts Set meter to measure DC Volts
Gain access to PCB (use Insulation Mat as required)
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

There is no need to wait for the fan purge to finish before commencing this test.
Measure the DC voltage between pin 11 on connector X5 and the earth on the incoming mains supply.
Expect either 0 vdc or 4.5 vdc.