Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to Resistance 
Remove tubes from APS noting their connections
Remove APS from boiler (top / rear of appliance)
Remove APS from boiler (top / rear of appliance)
Measurement:
Note the operating pressure indicated on the pressure switch.
Connect the air pressure switch charge kit to +ve connection on the air pressure switch.
Increase the pressure via the syringe to that indicated on the pressure switch.
Measure between the two terminals on the air pressure switch.
Expect continuity / zero resistance.
Note:
If continuity is not obtained when the specified pressure
is applied it is permissible to increase the pressure by 50%
100 Pascals = 1mbar / 50 Pascals = 0.5mbar
Connect the air pressure switch charge kit to +ve connection on the air pressure switch.
Increase the pressure via the syringe to that indicated on the pressure switch.
Measure between the two terminals on the air pressure switch.
Expect continuity / zero resistance.
Note:
If continuity is not obtained when the specified pressure
is applied it is permissible to increase the pressure by 50%
100 Pascals = 1mbar / 50 Pascals = 0.5mbar
Isolate as per TOPs P4
and refit as necessary