I just charged my a/c today after many years of running with the windows down haha. I now have cold air coming out, but with the control **** set to max a/c it eventually quits. I can hear the blower working it feels like the air is being diverted out the side vents of the dash. If I shut the truck off and fire it up, it works fine for a couple minutes. Is there a vacuum line that goes to the control **** for the damper doors? Or, a check valve in line possibly causing this issue? I know the a/c and heater are both working and blowing. Also, how hard is the fix? Thanks for the help.

 

What exactly quits, the coldness of the air or the air itself. If it's the air itself and the blower is still working and still set to max AC but air not coming out of any vents especially the defroster vents then it could be freezing the evaporator core (like trying to blow air through a block of ice) and perhaps it's not properly recharged. If the air is coming out of the defroster vents when set to max AC then you have a vacuum leak somewhere. Try turning the AC to VENT for a minute or so with the engine still running then back to AC and see if it is still the same, if the air has returned then it's probably freezing up, do you see water dripping from the evaporator drain all the time or only when you shut off the truck, if never then the drain could be plugged and you will see a condensation line on the heater plenum if you look under the dash on the pax side.

 

There is still air coming out cold, it gets diverted out of the side vents of the dash. When set to defrost, it does have cold air coming out of the defroster vents. It doesn't change if I set it vent and then back to a/c. The only time it will work right is if I shut off the truck and re-fire.

 

In the very back of the heater plenum driver side there is one vacuum actuator that has 2 lines going to it, it's the only actuator that has 2 lines, I forget what it's called at the mo but I suspect that initially it goes to the correct position with vacuum applied to only one port then because of a leak in the vacuum switch vacuum is slowly applied to the second line moving the door out of the selected position or the diaphragm is leaking internally and allows vacuum into the other chamber again moving it out of position.. Just a hunch I'll have to check the vacuum diagrams to be sure try selecting the system OFF then back to AC and see if that corrects it.

 

Do I have to tear apart the dash to get to the plenum?

 

On my 96 I had something similar happen. Mine turned out to be a vacuum line that ran across the top of the engine that I believe melted through on the exhaust manifold. It's evidently a common occurrence.

Bob

 

You can just see the actuator I'm talking about without removing anything. If you were to lose the vacuum entirely as with a leak it will go to defrost mode which is default and if that is not happening then you do still have vacuum, it costs nothing to check the vacuum line under the hood that feeds the ac control switch though, small black plastic line that goes through the firewall by the AC lines on the pax side.

 

Quick and easy way to check for vacuum leaks is to run the engine, shut it down for five minutes then disconnect any vacuum hose.
You should hear a hiss, if not you have a leak.
A leak free system will hold vacuum for hours if not days.

 

This is a piece to fix a known problem on the blend door. If you are going to get in there replace the old plastic piece too.

http://www.heatertreater.net/magento...php/dodge.html

 

I just wanted to give a big thank you to all the help and suggestions. I checked the vacuum lines and found some of the rubber deteriorated. Also, I found the vacuum line check valve to be fouled. I replaced the lines and the check valve and it works like a champ. It was kind of a pain to find the check valve. I found it at Autozone for $4.99. It is part # 47149 made by Dorman in the Help section. Thanks again for all the help it was very much appreciated.

 

Good find on the check valve.
My dealer didn't have a clue about it.