Set Appliance State:
Gas Off
Set Multimeter to Resistance 
Isolate Mains Power to appliance as per TOPs P4
Remove the two Grey wires from the air pressure switch and clip multimeter leads to the switch terminals
Remove the two Grey wires from the air pressure switch and clip multimeter leads to the switch terminals
| WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure |
Measurement:
Measure short circuit resistance with the Fan running.
Refit wires after test.
Note:
Resistance is measured with fan running at high speed
Refit wires after test.
Note:
Resistance is measured with fan running at high speed
Isolate as per TOPs P4
and refit as necessary