Set Appliance State:

Set Multimeter to Resistance Set meter to measure resistance
Isolate Mains Power to appliance as per TOPs P4
Remove the APS and assemble the test kit
Connect one of the tubes to the + connection on the telegan
Connect the other tube to the + connection on the APS
Attach probes/crocodile clips to the C and NO connections on the APS

Measurement:

Make a note of the badged operating pressure which can be found on the APS.
Apply the desired operating pressure through the syringe whilst observing the multimeter.
It is permissible to increase the operating pressure by 50%.
Expected reading is closed circuit.
Note:
Some APS show the badged operating pressure in Pascals:
100 Pascals = 1mbar