Living in florida I know a little thing about that problem the humindty sucks down hear.I was having the same prob with my pickup,went the autozone and the guy sold me this aerosol can that was made just for my problem it said.So I crunk the fan wide open on fresh out side air(that would be the panel setting)And sprayed it into the vent in the cowl were the air intake was located.Ran it for a while with the windows down ofcorse.Don't be afaid to use it liberaly it all evaporates without leaving a funky summers eve smell in you truck like lysol does....
