When I run my heat or ac through my dash vents while driving ,when I accelerate the air switches to my defrost and floor vents as soon as my rpms drop back down the air will switch back to my dash vents,sounds kinda strange,but I have heard of two other people with same problem.Any ideas what causing the problem?

 

Vacuum leak. check all your hoses and the check valves(passenger side of motor). If you have cruise control there is a hose under the battery tray also.BTW, you"ll want to check the whole system not just the heater/ac related hoses. Like the 4 wheel drive hoses, vacuum canister etc....

 

welcome to df. do a search on 'wild vents' and 'check valve' for a lot of posts, some include pictures.

 

Thanks for the info on the vent problems,I guess i better get busy looking for some leaks.