I have a smelly AC...

home or auto AC

if its your home AC you can put something that smells good in the return air behind your air filter like fragrance sticks or something. Also put a moisture absorber in there. Do you live in a humid area?

Thanks Gooch! It is a home AC and I live in sometimes humid NYC. I try to get rid of the origin of the smell (not to mask it). I tried spraying bleach to the "air in" part of the AC with a towel blocking the "air out" part. I think it worked a little while but the smell came back... ; (

Also you could have mold growing in the duct work. If you do this is a health concern. You should look inside of your ducts for anything moldy in there.