Cabin air filter (pollen filter)
Definition
The cabin filter sits in the HVAC fresh-air intake, usually behind the glovebox or under the scuttle panel, and traps dust, pollen, soot and insects before they reach the blower, evaporator and heater core; activated carbon versions also adsorb exhaust odours and ozone, and HEPA grades remove fine particulates. It should be changed every 15,000-30,000 km or yearly, more often in dusty areas, and is one of the most neglected service items. A clogged filter restricts airflow so the blower runs loud on high speed yet little air reaches the vents, windows demist slowly, the air conditioning seems weak because the evaporator is starved of air and can freeze, and the blower motor and its resistor or control module overheat from working against the restriction. A wet, mouldy filter (blocked drains, leaking scuttle seals) causes a musty smell on start-up and fogging. Fit the filter with the airflow arrow in the correct direction and make sure the housing lid seals, otherwise unfiltered air and debris bypass it and foul the evaporator. No fault codes; related symptoms are low airflow, blower noise, evaporator icing and odours.