Why does the air conditioner only work when you accelerate in your 2006 silverado z71?

Answer 1

While diving have a helper check all of the air vents. When not accelerating check to see if the cold air is coming out through the heater vent or the defroster. Most commonly the flapper doors that direct the air are moving into the wrong position. The doors are vacuum controlled so a vacuum leak is most likely the cause.