Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to DC Volts 
Gain access to PCB (use Insulation Mat as required)
| WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure |
Measurement:
Measure voltage across connection 2 (blue wire) and connection 3 (white wire) on connector marked X10.
Expected voltage 5 volts DC.
Turn DHW tap.
Measure voltage across connection 2 (blue wire) and connection 3 (white wire) on connector marked X10.
Expected voltage volts should drop to 0 (zero) volts DC.
Expected voltage 5 volts DC.
Turn DHW tap.
Measure voltage across connection 2 (blue wire) and connection 3 (white wire) on connector marked X10.
Expected voltage volts should drop to 0 (zero) volts DC.
Isolate as per TOPs P4
and refit as necessary