Where is the rear condensor located on a 1999 Suburban I am getting a drip behind the rear passenger side wheel but it doesnt smell like gas?

On my 1996 Suburban which is pretty much the same as you're 99. The rear condensor is located at the back door. When you open the door the shelf on the right side is removable. You will see the slots at the end of the carpeted area. That is where the rear condensor is.