Clean air is important for the cab just as much as the engine. Replacing the cab filter is simple with only a #30 torx bit, also known as a star bit and driver. If the cab didn't have a filter the heater core and the A/C evaporator could become plugged with lint, dirt and other air born debris, like they did years ago. That's why we need to change the filter, to keep us comfortable.
On a Cascadia the cab air filter is under the hood, just below the right hand windshield, to the far right. I will explain the process before you watch the video, so here goes.
To begin you need to visit your nearest Freightliner dealer, with the truck VIN in hand, purchase the replacement filter. Once you return to the truck, gather the tools, ( the #30 )torx bit and driver ) and open the hood. Using a step leader or standing on the right steer tire, as safely as you can, locate the filter cover, it's marked "cabin air filter". It's along the front of the cab in a large black trough. On each end of the cover is a small bolt and washer, this is were you will use the #30 torx bit. Using the torx bit, remove the bolts ( righty tightly, lefty loosey ).
Set aside the filter cover and locate the filter tray, it's down inside the housing about two inches. Take hold of the handle and pull up and toward the front of the truck gently, it will not come all the way out. You will see the old filter there, note the "air flow " direction arrow printed on the end of the filter. Remove old filter and, noting the air flow direction arrow, install the new filter.