Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Turn Hot Water Tap On
Remove 1 wire from the modureg and make safe
Gas On
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Reset appliance as necessary (Control knob to reset position for 2 seconds then release).
Allow the fan to run and observe the burner and spark electrodes through the viewing window (spark electrodes are located just to the left of the viewing window so it’s best to look through the window at a slight angle).
Does sparking occur and the burner ignite and establish smoothly?
Note: If the burner ignites it may take some time to fully cross light this is normal, as long as the burner remains alight and LED "B" illuminates the first outcome can be chosen.