Set Appliance State:

Mains Power Off
Use Insulation Mat as required
Set Multimeter to AC Volts Set meter to measure AC Volts
Turn Hot Water Tap On
Selector switch to Water
WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure
Mains Power On

Measurement:

Measure voltage between connection 4 (orange wire) and connection 1 (black wire) on connector X2 on main driver PCB.