Ok, to confirm, disconnect the hose where the red arrow is and put my thumb on the hose that goes back to the reservoir? Leaving the check valve still plugged into the engine side?


Unrelated, as I was explaining to my younger daughter all the repairs I was doing, including rebuilding the corner light attachment tabs stronger and better than before, she dubbed Ruby the "six million dollar VAN." 🤣

 

Until my service manual comes in the mail, I am stuck with bad mopar diagrams, but this is the duct system for the 99 ram van. #9 (two of them) are the actuators for the vents, #14 is the one for the blend door.




Looks like the one for the dash vents is the actuator on the driver side since they call it the panel vent and the other is the defroster vent? Would it be under/near the steering wheel and not in the doghouse?

It is too hot now to continue today, but since that is a $35 part that could probably stand to be replaced anyway I may try if it is easy to get to.

 

Keep the new valve in the intake under the dogbox a d disconnect the check valve behind the dash and put your thumb over the hose that feeds the interior check valve , the defrost foor should slam shut with your thumb over the hose . We know or at least are safe to assume the valve you ordered is good so leave it on the intake . All we are doing is taking it to the next valve to see if it's good . Thumb over the inside the cab vac line vents should blow , remove your thumb and the vents switch to defrost . If that is the case you know the inside the cab valve is questionable. My valves worked right with the blow method but turned out a new one solved the problem anyway.
if you ordered a service manual it is going to require a vac gauge and more than likely a pump . Harbor freight has their brand and also sells mighty vacs. I prefer the mighty vac but either is going to be essential to make sure you are not replacing good actuators

 

Thank so much again. I will check that tomorrow. Since the original check valve there is discontinued, is it crazy to try an aquarium check valve as a replacement since it is tiny like that one and may fit the hose? I guess for $2 it is worth a try.

 

Ok, I put my thumb on the hose below the dash check valve, and it did have suction but no movement on the vents.

I even replaced the check valve with the original lower valve, modified with connectors so it would fit, just in case the check valve was still the issue:

Still no change.
So as I understand it, it is probably the actuators that move the doors from floor to dash, as opposed to the door that moves the defrost door or the blend door from the heater. I can find all sorts of videos on how to replace the blend door actuator but not the panel vent actuator(s). The only pictures I can find are of older models with all metal actuators that have rusted stuck. Not entirely sure but I think my vent actuators and the actual doors have mostly plastic parts. I know the blend door one is.

I also looked into replacing the control switch (nit the blower speed, but the modes/max ac), but that is discontinued and nothing on the usual sites that sell old or used stock. But that is probably not the issue.

Even if I could find a video explaining this, I am almost certain those actuators can only be accessed by taking the whole dashboard apart. I will confirm this when my service manuals arrive. If that's the case, that is beyond my skill level and would be a very expensive mechanic repair. Boo.

 

Ok, first thing first: I saw a hack on youtube that miight apply here. Somebody with a similar issue in the same year ram truck ran a new tubing line from the intake to the check valve in the dash, and the dash vents opened. It was a very short video, but I assume this confirms whether the vacuum harness is bad. Should I try this or no?

Second, I have the service manual now, and I looked at the procedure for the floor-panel actuator. It does require dash instrument panel removal.


But I also see where the vacuum harness connects to it, and I think I can feel that end only from under the dash without instrument panel removal. Hopefully it is just disconnected because that would be an easy fix.

And I did see where the blend door lever was, and confirmed that moves with turning the dial to or away from AC so that actuator is not the problem. Even if it was broken, I don't think it would affect dash vents anyway:


Gonna try both tomorrow unless y'all tell me the hack is dangerous.

 

I have been fixing other things that has reduced the noise level in the van, and I revisited listening for hissing.

So with my ear right up to the hvac mode dial, I can hear faint hissing when put in any mode that involves dash panel vents. It almost sounds like it is inside the switch itself. I saw a video of a 96 ram 1500 truck where the switch was the issue - there was a rubber gasket in the switch itself that became loose, so when you turned the **** it would buckle and not make a good seal.

So I tried pressing on the back of the switch as I turned the ***** to see if maybe that would seal it and stop the hissing, and there was no change. I pulled it out a little too far and made a spark, so I quit. 😆

My hvac switch is totally different than the 96 truck one in the video I saw, but I can't help but feel like maybe the problem is in the switch. That part is discontinued but I found a picture of one ebay, and it looks like if I could find one, I would just have to connect the five color coded hoses since the electrical part is separate:

Does anyone know what the inside of this looks like, and if there could be a mechanical issue within switch to prevent a seal? Because I can't check the lines to the floor vent actuator without removing the whole dashboard, and I am not going to do that. And I don't think I would hear a hiss at the switch when the actuator is at least a foot away, right?

 

So I read up hissing at the switch could be the switch, or the line to the switch. I have my service manual so I know the red and brown lines go to the panel (dash vent) door so those are likely the problem somewhere.

So I decided to pull out the switch, take it apart and see if if anything looked wrong:

So the main body of the switch (1) has a spring (red arrow) and that looks fine. There is a gasket inside (3) that also looks fine, and shouldn't be slipping because it has tabs in the back to keep that from happening, but I glued it down just in case. Then the "lid" on the back (2) has the ports for the different color lines, and I can see through and blow through all the holes.

I let the glue dry and put it all back together, and reinstalled it, and there was no change.

I did notice on the end of the vacuum harness that connects to the "lid" (2) of the switch kinda looked unlevel. There are some depressions in it that are not on pictures of the part when it is new. So it might be that, or the colored lines in the vacuum harness itself:

This is pic of the new vac line I am getting off ebay since the part is out of stock everywhere. That big round end is flat except for the holes that you stick the ports from the switch into. It is also a different material (silicone maybe instead of black rubber maybe) so hopefully this will fix the issue.

If I can install it, that is. I need to see if the other ends connect above the doghouse and not in the part of the dash I can't get to without removing the whole dash. I think the red end does but not sure about the othe end. I am not going to open the doghouse until the part arrives.

 

I was checking pictures I took under the dash with the dog house open, looking for the connectors of the vacuum harness to see if I could replace it without having to take the dash off, and I discovered something I missed.

Earlier in the thread, I mentioned and posted a pic of a vacuum tube I found that went to nowhere. But what I missed was there was also a short brown tube behind it not connected to anything:

I thought, well there's my brown vacuum that goes to the dash vent. Where is the rest of it? And despite it being 95 degrees and the van parked in full sun for hours, I went in and took the dog house off. There was no "rest of the brown line". Somebody replaced it with black tubing (the tube that went to nowhere lol) and ran a new line routed different than the original, which is why I never thought it was part of the problem. I plugged them together and BINGO my dash vents work again.

It's so hilariously ironic it was what I originally thought, that I knocked a line loose replacing the blower switch, and that I had found it earlier but didn't know it. Well once again I took the long way ro get there, but now I can drive in the heat again without getting heatstroke.

Thanks everyone for helping me get there. Now I know if it ever stops working again (and I am sure it will), and it's not the same thing, exactly how to check all the lines and check valves, and I will have a new in package hard to find discontinued entire vacuum harness at my disposal if it all goes to crap. 😆

 

Awesome.

It was a roundabout process, but, I am going to bet you learned a fair bit about your van in the process.