Originally Posted by Gowgom,Jun 10 2009, 11:41 AM

Are you referring to the blower fan or the AC compressor cycling on and off? An auxilary fan kicks in when the compressor runs.

The sound (to me its more of a gurgling noise) I believe you are referring to is the refrigerant expanding in the evaporator which is in the passenger compartment. When it goes through the valve, it expands quickly and draws the heat out of the air passing through the evaporator.

This is normal.

I think it's more pronounced in our cars due to the tight quarters of the passenger cabin.

http://home.howstuffworks.com/ac1.htm

I hope that helps!