I lost my dash vent air...just blowing out of the defrost. I know that is the default if you lose the vacuum but I just am not sure where to start as far as tracing the lines out. I pulled the 2 vac lines off by the throttle body and had good vacuum there.
The connector plug under the dash by the actuator had no vacuum at any of the lines when I pulled that.
Any ideas where to look??

 

Haven't had this problem in my Ram, but have had with other cars. Search "vaccum leak" in the forum to see what others have checked.

 

Just had this problem on my Ram, if you are looking at the engine from the front of the truck. In the rear left of the engine bay, quite a few of the vacumm lines come together. One of my lines had broken in half and i was only getting air out of the defroster. I was having a heck of a time finding a new line(tried both parts stores and dealerships), so I ended up taping the line back together real good and it is working like it wasn't broken at all. Hope this helps.

 

Vacuum port on the right side of the intake manifold is the side that controls the a/c (among other things). Start tracing there. Test the check valve and then move back toward the firewall. There should be another check valve, test it too. From there, into the cowel. If no leaks/breaks found so far, you'll have to pull the cowel vent cover off and check the vacuum storage box. The line may have come off there (either entering or exiting), or the box itself may be cracked. From there it goes under the dash to the vac. distribution plug which you said you already checked.
Good luck.
WC

 

I'm guessing that this is a COMMON problem as I have the same issue, but mine only happens when I'm driving up a hill or kicking down the gas pedal, then I loose the vacuum. Any and all thoughts and answers would be a great help to ALL of us here I do believe. I haven't started digging as of yet as I was hoping to find all the answers first before doing so.

 

Was pouring out this evening so I will have to wait till tomorrow night to look.
How do you check the check valves? I did pull the vac lines off before the check valve and had suction there on both. Looking at the manual it has you using a test fixture that I do not have.

 

I followed the line to the vac reservoir and had suction there under the cowling. But still nothing at the the connector plug under the dash. If I read right I should have it on the black line at the connector plug. What is in between the reservoir and the plug??
UPDATE: Pulled the reservoir. Vac is fine there. Pulled the check valve and all is well. I see where the vac line goes into the firewall but cannot find it from the inside.Is the line going through the firewall with the ac tube the same one that goes to the connector plug?? Thisis friggin kicking my ***. Looks like I need to pull the dash to follow it now.

 

Bump

 

I am having this problem too on my `97 1500 Ram 2x4. It just started happening recently. I will check the vaccuum lines in the engine bay. I hope I don`t have to take the dash board out as a friend and I changed the evaporator a couple years ago.

 

If you have good vacuum at the reservoir but none at the multi-harness then the line between the two is broken somewhere. There is nothing in between them. Your options here are fixing the broken line (hard to get at) or the easier--replacement. To replace simply install a new tube from the reservoir, through the dash, and noodle it down to the harness.
WC