Ok people I have searched and can't find out how to get the AC/Heater knob to go al the way down! It's getting cold in Texas and the knob will not go all the way down. I do have a HU! It's like when I try to switch to the heater when you try to make it go it hot, it shoots back up to the middle their isn't a rock or anything that I saw and the vaccum also! What could be the problem?

 

I think I remember somebody posting on here once that the dealership replaced their ac control knob because there was a technical bulletin about it being hard to turn. Mine is very hard to turn sometimes, especially when you hit the point where your turning on the heat. Check with the dealership and see what they say.

 

^yep, there's a TSB out for it, dealership should fix it free of charge

 

Mines is hard to turn where the cold turns to the hot but they didn't fix it because it still worked. If yours is stuck and doesn't move then they should replace it.

 

It's actually the entire heater box under the dash that is defective. There is a TSB out for this. They replaced mine because the TSB states that if the knob is hard to rotate or is binding, replace the heater box. It's not a quick job, as they have to deplete the A/C and all that stuff.