If your AC drain is stopped up (usually courtesy of dirt dobbers)
then you will know it when you're taking a turn at the local red light and hear water flowing inside your truck.
If this is the case, I usually take a homemade tool that consists of a long and bent trans line. Set one end in the drain tube and take regulated air pressure from the other end. About 30 psi of compressed air will break loose whatever is stopping up your AC drain and the river will flow!!
Good Luck dude