The pollen filter is standard equipment in the Alfa Romeo 147. Its purpose is to help clean the air of pollen and dust before it enters through the air conditioning or heater system and into the cabin. Alfa Romeo recommends changing the filter every 20,000 miles, but this varies depending on location. Changing the pollen filter is a straightforward task that can be completed quickly and inexpensively.
Turn the windshield wipers on, and stop them at the 12 o'clock position.
Raise the bonnet and locate on the driver's side a small, circular plastic disc on the trim cover at the bottom of the windshield. Lever the disc off with a slotted screwdriver, then remove the screw underneath with a Phillips-head screwdriver.
Remove the foam block on the driver's side of the engine compartment below the bonnet lifter. Pull the foam block up and out of the engine compartment.
Grab the rubber seal strip that runs across the top of the engine compartment, below the windshield; pull the part of the strip that's on the driver's side off the metal rim. There is no need to remove the whole strip.
Remove, with an Allen wrench, the two screws under the seal strip that secure the pollen filter cover. Lift the cover up and off the filter compartment; don't pull too hard as the windshield washer hose is connected to the cover also.
Remove the rubber strap that secures the filter over the air conditioning/heater duct and lift the filter out.
Install the new filter, taking note of the air flow directional arrows printed on it; they should point down. Replace the rubber strap to secure the new filter.
Replace the pollen filter cover, and the retaining Allen-head screws. Replace the rubber engine seal strip, and the foam block. Install the Phillips-head screw to the trim under the windshield and secure it; then replace the circular cover trim.
Lower the bonnet, and return the windshield wipers to their correct position.