horrible smell with air conditioner

[Deana]

yes, it's January and we still sometimes run our a/c. I have noticed, for the past two months or so, that when I turn on the a/c, there is a horrible smell coming from the vents. It almost smells like moldy towels or something like that (but REALLY strong). There is no odor if I only run the blower (no heat or a/c, just the overall house fan). There also is no odor when we have the heat on.

Any thoughts???

[ParagonEos]

I dunno Deana, Maybe you should call and ask a professional, that just doesn't sound good.