dadmomh wrote:
The furnace in our ROO - Suburban, I think but can't be sure, did not have a filter in the air return, only in the ceiling unit. It was a sponge-type material. I just took it our 3 or 4 times a season, gave it a squirt of Dawn, squished it around and rinsed and dried. I recall someone who used a filter in the return even though the manual specifically said not to....I'd be leery of doing that. Our return on the ROO was under one of the dinette seats and it was a quick job to lift the plywood and vacuum it out. With our TT, it's under the cabinet below the kitchen sink, even easier to get to.
OP is talking about the filter in air return for his A/C unit...not his furnace.
RV furnaces don't use filters.