Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to DC Volts Set meter to measure DC Volts
Remove the i-controller (display pcb) from the front of the boiler
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Measure the voltage between pins 1-3 on the right hand connector to the display pcb and the neutral at the incoming mains terminal strip.
The Voltages should conform approximately to the table below:
TestDC Volts
111.7
2 0
315.3