sound of air conditioner

I have a Crosley air conditioner and it just started to make a sound similar to putting a card on bike spokes. That fluttering sound. What would be creating this? It's not overly loud but is apparent. My other air conditioner is not making that sound.

: I have a Crosley air conditioner and it just
: started to make a sound similar to putting a
: card on bike spokes. That fluttering sound.
: What would be creating this? It's not overly
: loud but is apparent. My other air
: conditioner is not making that sound.

It could be the normal sound of the rear condenser fan blade picking up the moisture that pools in the air conditioner's base. This water (recovered from the room humidity) is often slung against the hot condenser to help in the refrigeration process.

It is also possible that something is lodged in one of the fan blades or one of the fans has broken and is now hitting its shroud. Lastly, if you ran the unit overnight, perhaps frost has built up on the front evaporator (cooling) coil and the fan there is hitting it.

Dan O.