I have a 1995 Dodge Ram 1500 4 x 4 with a 318 cu. in. When I accelerate the A/C goes from blowing through the A/C vents to blowing through the defroster vents. Then when I take my foot off the gas I can hear the valve switch back to A/C vents. I really notice it when I am pulling my trailer. When driving around town you could hang meat in the cab it only happens when I am going around 45 th 50 mph. I did install a hypertech module to increase my power. Is that maybe the problem? Any advice on what to look for would be greatly appreciated. Thanks

 

Gavult! It never ends! lol
I don't even want to get into the meat in the cab thing. haha!
You've got a check valve problem. A search using any terms like vacuum, defrost, or any symptoms will come up with the answer but, I'm in a frolicking mood so...http://dodgeram.info/tsb/1996/24-01-96a.htm
Welcome, and have a happy!

 

I found a vacuum line unhooked under the hood. Still doesn't work right. I can hear a whistling noise inside of cab now. Where is the vacuum line to the blend door located? Thanks

 

Blend door is electric. Unfortunately, the other control doors can't be acessed easily with the dash on.

 

I assume, maybe wrongfully so, that by blend door you mean the **** that controls your temperature. If so, that door is controlled by a cable. I just had my box out not long ago and it has a cable that attaches to the top of the box via a screw and clip. Just my two cents!

 

I just assumed it was the blend door opening and shutting I can hear a door opening and closing around my feet or center of cab when I accelerate. Are there any vacuum lines in that area? Thanks

 

There is a plug under your dash around the box where your vaccuum lines hook together. Make sure that plug is together. All you vents other than your blend door are controlled by vaccuum. You have a vaccuum line coming through your firewall where your ac lines come through. That line will run to a check valve on your intake. Sometimes this may have come unhooked or your check valve may be bad.There are all kinds of articles on here about how to diagnose your check valve. Sounds like you definitely have a check valve / vaccuum issue.