I want to document this to help others who need to find their vacuum lines as well. I find lots of clues in old threads and this will be my legacy lol.Lets start with this, you want to find the reservoir (#4) and trace the line (#5) from there:


For my 1999 dodge ram van 1500, you can see the reservoir if you remove the headlight globe:


If you look down from the top with the headlamp removed, you can see where the lines go:


In my van they put both lines into a mesh sleeve after it went through the (speed control servo? ) and ran it to the dash differently than the diagram. It ended up near the top of the wall but I can't see to where they connect to the dash from topside. They are the lines that form a V shape::


I made a quick video tracing the line as far as I could see it from above:
https://drive.google.com/file/d/1WqLI5q1-vBpn4icjeRYU02KnWM-vceas/view?usp=drivesdk

The two lines are the speed control cable and the vacuum line. Another diagram I found helpful:


In my case the lines look fine, but the sleeve may cover something I can't see. My money is on the other end, where it is either not connected securely or the aforementioned check valve is bad.

I will crawl under the van to keep looking another day, when it is not ridiculously hot.

 

I got the idea I could stick my phone down where I could not see the lines and take pictures in night mode. So while I could not see where it connects to the dash or the check valve, I could see a little further where those two lines go:


And I notice weird shadows on the one I think is the vacuum line. So I zoomed in and saw this:

That looks cracked to me!

So from what I understand, because I don't have anything on hand to fix this but duct tape 🤣, I need to cut out the bad part and stick the good ends into this to connect them:

which is in stock at my local auto parts store. I don't know the tubing sizes involved so this kit will help me figure that out.

And I probably need to look and doublecheck under all of the sleeve holding the line before I go because maybe there are more cracks under there.

If that doesn't work, then finding the check valve and rest of the line will have to involve removing the doghouse for my particular van. I don't really want to do that, it is haunted. So here's hoping this works.

​​​​

 

Yep that's the resivour , the check valve on the intake does involve taking off the dog box. Always a joy . When I was checking everywhere for a leak before I found the check valve on the intake I traced a few lines down towards the charcoal can and there are a few that after looking online that actually go no where , they are vents they put up high to avoid being plugged with mud . Don't let those ones drive you mad .
I couldn't find a leak anywhere and lines were in goid shape but I still went over them with a propane torch unlit . If one is sucking air you will hear the rpm change when you are over the leak .

 

I am still waiting for the check valve to come in the mail, so I haven't opened the dog house yet. But in the process of fixing other things, I have replaced all the relays in the fuse box and it had no impact on the ability to blow through dash vents. So it is hopefully just the cracked hose and maybe the check valve. I believe I will be able to see the actuator while in there so I can look at that too.

I really want to get this done because it sucks to not have front vents in 90+ degree temps.

 

I have a limited window in the morning to work on the van because it is so hot right now. But today I was able to take off the doghouse and get a first look. It was so dirty I took most of my available time to work to clean and take pictures of what was where.

I did find the check valve under the dash:


And I also found this hose to nowhere. Not sure if that is supposed to be a vent, or supposed to be connected to something:



And I also found a bunch of tree debris in the airfilter, which I am not if that could lead to clogs in the lines that affect the dash vents. I used to park under trees but I stopped one I realized they were pooping right into space between the windshield and the hood.


But I couldn't find the line that was cracked from this direction before it got too hot:


So tomorrow I will try to mark it from the hood side if I can so I can look for it in the doghouse. I may also just change out the check valve just to rule it out. Hopefully I put it in the right orientation lol.

 

So this morning I went back under the hood, found the cracked line on the vacuum harness, and marked it with red tape so I could find it from the doghouse side. This is the line:

Visually it looks pretty good. I want to patch the bad part before trying various other methods to check the rest of the hose. So before I proceed with that...

I just cut out the cracked part and connect the ends with the bigger hose? I also have a vacuum elbow, can I use that instead to connect them? I have a lot of experience with drip irrigation systems so that is something I know I can do correctly.

Also, is that large disc between the two elbows in the lower left corner the other check valve? If I replace it, how do I know which end goes where?

​​​​​Thanks again for your guidance. I really want to do this correctly.

 

I generally just use a piece of rubber line the appropriate size. Works great.

 

Ok, I cut out the piece that may have been cracked (hairline if it even was cracked) and stuck the two good ends snugly in the bigger connector tube. I did confirm that piece I asked about was the second check valve and replaced that. And I changed the air filter. Started the van up, ran fine but no change in the vents.

I pullled the check valve in the dash and blew into it, and it seems to work. I don't have a replacement as it is different than the one I replaced near the engine.

It only blows through feet and blower, and feet instead of dash in all positions. It occasionally makes a rattling vibration sound, but the may be compressor related (and that is on its last legs)

So it is the mechanism that directs the vents, which could be mechanical or electrical? If it's the blend door or actuator, I am not sure I can fix that myself.

 

That is the check valve in the lower left , if it has an arrow on the replacement point it at the intake , if not blow through it and put the end that you can suck through facing the intake .
if you want to tell if it is your problem just pop that valve off and blow or attach a mighty vac to it , if one way is not a dead stop its your problem . One way you should not be able to draw any air past .
Yes the vac lines are like drip emitters, cut , splice or shrink wrap ends, liquid electrical tape works pretty good also or plastidip . If its an easy shot replace the whole line with rubber vac hose . Just don't want any leaks !

 

The actuator on mine was under the dash around the controls. The lower part of the dash cones off with a few screws and gives you a good look at it . Never had to replace mine but it didn't seem too hard if it were my problem when I was tracking it down. Also with the good valve on the intake , putting your thumb over the end of the hose that leads to the inside check valve should make the vents blow . If not I'd look I to how to test the actuator , a mighty vac goes a long way testing vacum problems . Or at least confirming you need to look elsewhere