Your cab’s fresh-air filter keeps dust, hair, fibers, and other impurities from clogging heat exchangers and the evaporator core—and cleans the air that you breathe. Inspect the filter using the same mileage or operating-hour schedule you use to schedule your oil changes. If you can’t shine a flashlight beam through the paper pleats, it’s time to replace it with a filter that meets the original-equipment spec. Read more HVAC maintenance tips from Red Dot Corp.