It should be cleaned every one to two years, depending were you are. Its not a quick job, I have to remove the whole housing and the fan on my unit. I deal with alot of dead leaves, I finally bout a cover for the off season, made a hell of a difference.It could just need to be cleaned if its got 20yrs of dust on it but u gotta remove other parts to access the blower motor to check/remove it! Plus disconnect the wiring from it so more chances i could mess something up trying to do it myself!