Set Appliance State:

Set Multimeter to AC Voltage Set meter to measure AC Volts
Turn Hot Water Tap On
Isolate Mains Power to appliance as per TOPs P4
Boiler Operating Switch / Programmer set to WATER only
Gain access to the PCB (use insulation mat as necessary)
WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure
Mains Power On

Measurement:

Measure the voltage across connection 3 (Brown wire) and connection 2 (Blue wire) on connector X6 on the main PCB.