Set Appliance State:
Mains Power Off
Set Multimeter to DC Volts 
Turn Hot Water Tap On
DHW temperature set to MAX
Selector Switch in Hot Water Position
Selector Switch in Hot Water Position
| WARNING! - Mains voltage is expected during test follow TOPs P4 live testing procedure |
Measurement:
Allow burner to ignite and establish.
Measure the voltage between the red and violet pins marked 1 and 2 on connector X6 at the PCB for at least 1 minute.
Voltage should remain at approximately 50V DC.
Measure the voltage between the red and violet pins marked 1 and 2 on connector X6 at the PCB for at least 1 minute.
Voltage should remain at approximately 50V DC.
Isolate as per TOPs P4
and refit as necessary