Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to AC Voltage Set meter to measure AC Volts
Boiler mains switch ON
Ensure secondary heat exchanger is cool and there is a demand for Preheat
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Measure voltage across brown lead (live) and pink lead (neutral) at PCB side of inline connector.