Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to Resistance 
Remove the wires and tubes from the air pressure switch (noting their locations)
Connect the APS testing kit and FGA to the APS (positive connection)
Connect the APS testing kit and FGA to the APS (positive connection)
Measurement:
Steadily increase the pressure using the syringe to that shown on the APS.
(pressure may be shown on rear of APS, remove / loosen securing screw to view)
Measure the resistance between the common and normally open terminals.
Continuity / zero resistance should be measured.
Notes:
1. If continuity is not obtained it is permissible to increase the pressure by 50%.
2. 100 Pascals = 1mb / 50 Pascals = 0.5mb.
(pressure may be shown on rear of APS, remove / loosen securing screw to view)
Measure the resistance between the common and normally open terminals.
Continuity / zero resistance should be measured.
Notes:
1. If continuity is not obtained it is permissible to increase the pressure by 50%.
2. 100 Pascals = 1mb / 50 Pascals = 0.5mb.
Isolate as per TOPs P4
and refit as necessary