Like I said above, it's not the knob being stripped and not turning. Any ideas?

Like I said above, it's not the knob being stripped and not turning. Any ideas?

What year is it? Could be that the actuator is worn out.

//2000CAYukon

2003

Mine has a dial on the right you turn to change they have many vacuum lines on the back. They are $57.00 at the dealer. If you pull it out it has contacts as you turn it. I would check they have proper tension and clean the surface with contact cleaner or brake clean. The plastic piece comes out with a screwdriver be very careful and don't break it. Then unbolt the unit so you can get to it.