Set Appliance State:
Set Multimeter to AC Volts 
Turn Hot Water Tap On
Isolate Mains Power to appliance as per TOPs P4
Gain access to PCB (use insulation mat as necessary)
Gain access to PCB (use insulation mat as necessary)
| WARNING! - Mains voltage is expected during test follow TOPs P4 live testing procedure |
Measurement:
Measure the voltage between the brown and blue wires at connector M15 on the main PCB.
Mains voltage should be present.
Mains voltage should be present.
Isolate as per TOPs P4
and refit as necessary