Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to AC Volts Set meter to measure AC Volts
Turn Hot Water Tap On
Selector Switch to Hot Water
Gain access to PCB (use insulation mat as necessary)
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Check AC voltage at connector X3 pins 5 (Black) and 7 (White).
Expect mains voltage.