This is the smog sensor inside the ventilation casing. It is used to turn on charcoal filter or put the car to ‘recirc’ in polluted environments.

A look at the ventilation casing when cover is taken off. Clean out leaves and other dirt while open.

A new filter and the old. This is the charcoal version with a layer of charcoal on the underside.

Blower motor with fan. The black little box on top is the regulator the controls the speed of the fan. This can overheat (perhaps from a clogged filter) and fail, letting the fan to operate on single

Clogged filter can put so much strain on the fan under, that the fan can fail, not being able to ‘suck’ air.