Set Appliance State:
Set Multimeter to AC Voltage 
Turn Hot Water Tap On
Isolate Mains Power to appliance as per TOPs P4
Selector Switch in OFF position
Hinge down the electrical box and remove small PCB cover
Remove cable clamps and move cables to allow access to control board below
Selector Switch in OFF position
Hinge down the electrical box and remove small PCB cover
Remove cable clamps and move cables to allow access to control board below
| WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure |
Measurement:
Test 1:
Place probes on the multipin plug outlet from the control board across connection 3 (white wire) and connection 6 (yellow wire). Turn selector switch to DHW. Voltage measured should be approximately 15V AC.
Turn selector switch to OFF position.
Test 2:
Place probes on the multipin plug outlet from the control board across connection 3 (white wire) and connection 5 (orange wire).Turn on selector switch to DHW. Voltage measured should be approximately 24V AC
Place probes on the multipin plug outlet from the control board across connection 3 (white wire) and connection 6 (yellow wire). Turn selector switch to DHW. Voltage measured should be approximately 15V AC.
Turn selector switch to OFF position.
Test 2:
Place probes on the multipin plug outlet from the control board across connection 3 (white wire) and connection 5 (orange wire).Turn on selector switch to DHW. Voltage measured should be approximately 24V AC
Isolate as per TOPs P4
and refit as necessary