Last updateWed, 18 Oct 2017 10am

On The Road

Make sure to check cabin air filter on a regular basis


Q: My air conditioner hasn’t been working well at cooling my car down. Every time I turn on either the heater or air conditioner, there is a foul smell. I went to a nearby auto repair shop and was told that nothing was wrong with the air conditioner – I just need a new cabin air filter. I am skeptical about that, and I wonder what a cabin air filter is and how that could fix my problems.

A: Despite the fact that most vehicles today have filters that clean the air entering the vehicle passenger compartment, the cabin air filter is one of the most overlooked service items. It is important to understand that failure to change this filter periodically will have adverse effects on the health and safety of the vehicle occupants, reduce the efficiency of the vehicle’s heating and air-conditioning system and even hasten the demise of certain vehicle parts.

This filter is located in the air intake for the passenger compartment and filters dust, pollen, dirt and other allergens from the incoming air. At the same time, it prevents leaves, bugs and corrosive debris from filtering into the heating, ventilation and air-conditioning systems, which would affect performance. The buildup of leaves and debris is usually the cause of the foul smell you are experiencing.

There are different types of cabin filters to fit most vehicles. The standard filter traps most particles larger than 3 microns in size. A better filter is electrostatically charged so that it can trap particles as small as 0.3 microns. The best of the cabin air filters contain activated charcoal, which helps remove odors, fumes and gases.

The easiest way to determine whether a vehicle has a cabin air filter is to check the owner’s manual or ask a service technician. These filters are usually located behind the glove box or under the hood near the base of the windshield, and are reasonably easy to change.

Not changing the filter results in a gradual buildup of contaminants, which will prevent it from properly filtering the incoming air and result in foul smells, bacteria and allergens entering the passenger compartment. Additionally, when less air is able to pass through a clogged filter, it negatively affects the performance of the air-conditioning/heating system and makes the components work harder, leading to a shorter useful life.

The technician who looked at your vehicle is most likely correct – make sure your cabin air filter is checked and changed regularly, based on your manufacturer’s recommendation.

Warren McCord is an ASE Certified Master Technician and owner of Dean’s Automotive Inc., 2037 Old Middlefield Way, Mountain View. For more information, call 961-0302 or email McCord at This email address is being protected from spambots. You need JavaScript enabled to view it..

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