My 01 will stay on defrost even if I turn the dial to other settings. It doesn't matter if the blower is on low or high, all that I get is defrost. Someone once mentioned it was caused by a vacum leak. Not sure if this is correct of not. Has anyone else had this problem? With the temps in the 20's and 30, using only defrost to heat the truck in the morning isn't a lot of fun! Thanks for the help.