All the a/c maintenance / efficiency blurbs talk about changing filters, without specifying whether they mean some filter built into the a/c, or the central system filter that is used by the furnace too (or both).
I couldn't find a filter in the meager literature that comes with our a/c, or that I could see on the a/c unit.
Is it there a filter on some/all a/c units, or are they refering to the regular central air filter?
thanks