Set Appliance State:

Mains Power Off
Set Multimeter to DC Volts Set meter to measure DC Volts
Turn Hot Water Tap On
WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure
Mains Power On

Measurement:

During the sparking stage of the ignition cycle measure the DC voltage between pin 8 (Red) on connector X25 and a suitable earth.
Expect approximately 15-22 Vdc.
Note:
Each pin on the PCB connector is numbered.