I discovered a problem with my cruise control while driving my 1996 Ram 4x4 across country this weekend.

If I have the AC running and the cruise control set, everything seems to be working fine until I start to climb a steep grade. The cruise control seems to hold speed, but the AC switches from blowing out the dash and starts blowing out of the defrost wents. If I step on the brakes it returns to normal.

I am not sure if this is a vacuum problem, or what, and any advice on where to start looking would be great.

 

So do you have an a/c problem or a cruise control problem?

 

I assume that it is a cruise control problem.

If I keep the cruise control turned off, the AC works just fine, regardless of how steep of a hill I am on.

 

Check your vacuum hoses under the hood. May have one cracked or loose. They are plastic tiny lines.Your loosing vacuum somewhere, which changes the door in the dash.