Air changing from vent to vent.
Hi. I have a 1998 Ranger and when the air is on, and I am going down the road, it changes from vents to defrost then slowly goes back to vents. It does this only when I am giving it gas, at idle it is fine. It has a 2.5l engine. I read the other posts and checked the vacuum hoses and they seem to be in place. I would appreciate any help you can give me.