Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to AC Volts Set meter to measure AC Volts
Turn Hot Water Tap On
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Allow burner to ignite.
Measure the voltage between the brown and blue pins on connector CN9 or CN08 (dependent on which version main PCB is fitted)
Expect mains voltage.