15000 btu A/C slight knocking sound

[bigcuzauto]

My 15000 btu ducted air conditioner started making a slight knocking noise this weekend. Its not overly loud but something does not sound right. Any one have some ideas? I do have some time left on the warranty and can bring it in for service. It can be heard if you stand under the unit inside while running. If you open the room dumps the noise can no longer be heard. I assume it is still there I just can not hear it any more. I did not try to switch fan speeds, may be something to try? Thanks for any input you may have.

[PonyExpress]

open the door and let em in!

[spoon059]

I have to wonder if its something in one of the ducts, just banging around. Take it to the dealer, let them figure it out.