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
Gain access to PCB (use Insulation Mat as required)
Ensure a flow rate of 3 litres per minute
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Measure for DC voltage across pin 6 (green lead) connector X2 and
a suitable earth connection.
Expected voltage approximately 2.3 Vdc (voltage may fluctuate).
Note.
Ensure a good connection is made or misdiagnosis may occur.