A periodic maintenance item for any vehicle is to replace the cabin air filter, for the dash AC.
I must admit, I thought our coach didn’t have a replaceable filter, until pointed out on my Tiffin Allegro Bus 2016-2018 Owners Facebook group. Oops.
Here’s a picture of where it is located in the generator compartment, for context:
It’s rather difficult to get out (update: it’s actually easier than this; I had only unclipped the bottom, but when I changed it for the second time, I realized there’s a clip at the top too, that was buried under insulation):
Ours was definitely overdue for replacement:
(Update: the guys at Bay Diesel in Red Bay were interested in the filter I used; they said it was much better than the one they had sourced.)