Set Appliance State:

Gas Off
Turn Hot Water Tap On
Isolate Mains Power to appliance as per TOPs P4
Connect the air pressure switch charge kit to +ve connection on the air pressure switch
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 fan to run.
Once fan begins to run increase the pressure via the syringe to that indicated on the pressure switch.
Sparking should then be observed at the electrodes.
Note:
Wires to APS must be reconnected from previous test.