Changing hvac filters

Most of those panels snap in and out

 

If there aren't any screws that's the way to do it

 

Theres got to be a dealer open you can call the service department and find out before you bust something.

 

Never personally changed one in a 4900. But here is diagram I found for a 2014 4900. It looks like there is only one fastener.

 

Mine pretty much falls right off when I remove that one screw?

Gotta add....doesn't Western Star have the absolute worst cab air filter setup there is? The filters are useless. And for a vocational truck, you would think they would make them easier to change.
I even buy the upgraded washable filters and my dash is still covered in road salt after one trip. You don't dare put the fan on high or the dust storm will choke you.

 

I just changed the filters in my 2012 4900fa for the first time. Trucks got 350,000km on it. They were dirty and needed to be changed. They were doing there job, the heater core looked clean as can be.
Popped 2 new filters in there goodtogo!!

I don't mind there setup, seems to work good.
Keep in mind I'm also the kind of guy who turns the a/c on reserculation when I'm in a dusty jobsite.