Set Appliance State:
Mains Power Off
Use Insulation Mat as required
Set Multimeter to DC Volts 
Turn Hot Water Tap On
Selector switch to Water
| WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure |
Measurement:
Measure voltage between connection 7 (red wire) on connector X20 on sequence board and neutral X4 on main driver board.
Isolate as per TOPs P4
and refit as necessary