Belts loosening when new
 

I have a 2001 GT. Sometimes when the a/c comes on I hear it cycle, sometimes I don't. Actually when I hear it cycle, I can feel it too, kind of a "tink". It has less than 500 miles on it and I was wondering if the a/c belt or tensioner needs to be tightened. Most of thet time I cannot feel or hear the thing, which I think is what it is supposed to be like. Or, very, very slightly I can feel it, but not hear it. Any suggestions?
Thanks