We live in a rented mobile home in Texas; the landlord requires us to change filters once a month in the heat/air unit, which is a Coleman Evcon. (There is no model number visible.) The filters were sitting tilted along the side, inside the case, when we moved in. We have lived here over a year and have never removed a dirty filter! When we take them out, they're as clean as they went in. We continue to change them as required, but we're wondering if they are where they :should: be. If anyone can tell us WHERE those filters are supposed to be (my husband suspects there should be something at the top, where there is a grating that is always dirty) it would be a great help.