Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to AC Voltage Set meter to measure AC Volts
Gain access to PCB (use Insulation Mat as required)
Selector switch to DHW position
CH temperature selector to Min
DHW temperature selector to Max
WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure
Mains Power On

Measurement:

Measure voltage across connection 6 (yellow wire) on connector X3 on the main and a suitable neutral.