If you take the inside cover off to get to the bolts, you will likely see how the warm, moist air from the intake can contact the cold surfaces.
Maybe next rain, drop the cover, find source of water?
Lazy man idea about re-installing the 4 bolts; (Young person may have no issue, but many in my age group have problems working overhead) They are long, for diameter, and not a lot to guide the top end to hole. And while you are trying to get them started, you are holding the plate up and in place. I took a couple pieces of all-thread (1/4-20, IIRC) longer than bolts, screwed them into holes. Much easier to start nuts, and the studs hold plate up while start 2 bolts. Double nut to remove studs, replace with bolts
