I had a problem with my heater cable slipping. Took it in 2 times and they said it was fixed. The third time they said that it was the best that they could do. I found that I have to turn the knob very slowly or it will slip.
2005, blue crew cab, Z71 LS, 4x4, sunroof, remote snug top LS, Airaid intake w/throttle body, Mr. Head Light, Matching Blue X-liner, PCM tuned