Set Appliance State:
Mains Power Off
Set Multimeter to DC Volts 
Turn Hot Water Tap On
Use Insulation Mat as required
Selector switch to hot water
DHW temperature selector to maximum
Selector switch to hot water
DHW temperature selector to maximum
| WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure |
Measurement:
Measure the voltage across the blue (-ve probe) and white wires (+ve probe) on J6 (black connector) on main pcb. 0 V DC should be measured.
Turn hot water tap Off.
Repeat test. 5 V DC should be measured.
Note:
For this test it is easiest to use the front of the connector where exposed silver connections can be seen to make the best connection.
Turn hot water tap Off.
Repeat test. 5 V DC should be measured.
Note:
For this test it is easiest to use the front of the connector where exposed silver connections can be seen to make the best connection.
Isolate as per TOPs P4
and refit as necessary