Heater has no airflow (W6E/W15E)

The Leister is not getting enough cooling air.

This air goes through the black hose to the bottom of the heater.

It is blown out by the fan mounted on the back of the partition wall.

The airflow is monitored by a pressure switch on the right side wall (viewed from the back, so on the left).

What to check:Search for the cause of the lack of flow.

Is there really too little flow, or is it just not being measured correctly?

Has the machine worked properly before?

Has anything changed/happened before the machine stopped?

Is the black hose (located in the back of the machine) still intact? Is the black hose properly connected?

What happens if the filter is not on the fan?]

Does the fan rotate (in the correct direction)? What value is the pressure switch set to (110S5)? 

This should be at least 8 mbar on a properly functioning machine. They should be leaving here at about 10 mbar.