The AC in my 06 silverado 1500 with 1200 miles is making an annoying hissing sound that mainly occurs when the temperature inside the vehicle is close to what the automatic electronic control is set to and when i am at low speed or stopped. Any ideas what is causing this and if it is repairable.

your warranty was expensive (built in the price) . enjoy it while you can.

A hissing sound coming from the center a/c vents usally indicates that the system is low on refrigerant.