Probe stuck on defrost

[irkorn18]

I have checked all that I can possibly find and I don't see anything wrong with any vaccuum lines, I has my a/c on, then I turned it to vent, and out of no where my defrost is the only thing air will blow out of, my dad's 01 Grand Cherokee has the same problem...any suggestions?

[Davescort97]

The heater/AC goes to defrost by default when there is something wrong with your system. It's designed this way so that you will always have defrost because it is a safety matter. I suspect the vacuum diaphragm is ruptured if all the vacuum lines are all right.

[irkorn18]

I was thinking I heard something about that's the defualt setting....what is the part you are talking about is ruptered, I've never heard of it...is there anything you can think of to help trace the cause..?

[Davescort97]

The part that controls and moves the door(s) in you heating A/C system is vacuum operated. Some call it a vacuum motor. It has a vacuum port on one side and a lever on the other side to control the door's position. There is a membrane in the center to be moved by the vacuum applied to it. The fact that your system is on defrost pretty much narrows it down to this vacuum motor.

[irkorn18]

Awesome, alright, well, I'll look for it, hopefully it's in my Hanes, I'm going to go see about getting it done right now, would it be ther motor that's bad? Or what all would need to be replaced, in general?

[Davescort97]

The vacuum component is one of the things it may be. The other may be the blend door is worn out on it pivot points.