Set Appliance State:
On/Off Switch OFF
Set Multimeter to AC Volts 
CH Demand
Isolate Mains Power to appliance as per TOPs P4
Gain access to PCB (use insulation mat as necessary)
Gain access to PCB (use insulation mat as necessary)
| WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure |
Measurement:
Measure the voltage between the top pin (brown) on connector CN1 and a suitable earth.
Expect mains voltage.
Expect mains voltage.
Isolate as per TOPs P4
and refit as necessary