Set Appliance State:

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

Measurement:

Measure voltage at connection 3 (brown wire) and connection 4 (blue wire) on connector CN7 on the main PCB.
Note: On some PCB's the connector will be labelled as CON4 not CN7, however the test points and the colours of the wires stated remain the same.