Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to Resistance 
Remove air intake pipe
Remove the 2 black wires from the low pressure switch
Remove the 2 black wires from the low pressure switch
Measurement:
Measure the resistance between the 2 terminals of the low pressure switch.
Expect continuity / zero resistance.
Is the resistance measured as expected?
Expect continuity / zero resistance.
Is the resistance measured as expected?
Isolate as per TOPs P4
and refit as necessary