I have a 02 gmc and i cant control my heater/ac it just blows cold air. i bought a new climate control box that goes under the radio and that wasnt the problem. Have no idea where to start looking i have checked fuses in the fuse box but no luck:confused: ..... Has anyone had this promblem any ideas? Thanks

Check the temp blend door for obstructions, and check the blend door motor for proper operation.