Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to DC Volts Set meter to measure DC Volts
Turn Hot Water Tap On
Pull connector X6 back slightly to expose test points
Set flow rate to 3 litres/min
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Measure the DC voltage between pin 6 (blue) and pin 5 (black) on connector X6.
Expect approximately 3.3V DC.
Note:
Voltage may be seen to fluctuate slightly.