Set Appliance State:

Gas Off
Isolate Mains Power to appliance as per TOPs P4
Connect the air pressure switch charge kit to +ve connection on the air pressure switch, disconnect the -ve connection and ensure performance tester reads 0mb before continuing
Reconnect wires and refit APS if you have not already done so
Selector Switch in Hot Water Position
WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure
Mains Power On

Observation:

Note the operating pressure indicated on the pressure switch.
Allow the boiler to begin it's ignition sequence.
Approximately 2 seconds after the fan starts
to run increase the pressure via the syringe
to that indicated on the pressure switch.
Can sparking now be observed
between the ignition electrodes?
Note:
100Pa (Pascals) = 1millibar
If sparking does not occur it is permissible to increase the pressure by up to 50%