Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to DC Volts Set meter to measure DC Volts
Pull X4 back slightly to expose test pins
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Measure the voltage between pin 5 at X4 to a suitable earth point.
Voltage should be approximately 25V DC.
Repeat for pins 1 through 4, voltage should be 25V DC on each pin.