Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to Resistance 
Disconnect the fan - air pressure switch connector
from the pcb (5pin - connector)
from the pcb (5pin - connector)
Measurement:
Measure for continuity between the air pressure switch
leads and the disconnected connector as listed below.
leads and the disconnected connector as listed below.
| Leads | Resistance | Grey - Grey | Continuity (zero resistance) |
| White - White | Continuity (zero resistance) |
| Black - Black | Continuity (zero resistance) |
Isolate as per TOPs P4
and refit as necessary