What are you driving?

 

1998 Ram 1500 5.2

 

Grab the service manual for your truck from here.

 

Grabed those the other Day, I am thinking that it goes to the cone shaped end of the vacuum Valve in the engine bay as there is nothing on it now, the other end is the top plastic line as they come through the firewall, there is no bottom line near the evaporator.
I think also I have the same issue you were talking to a guy about in another thread where the plastic line is broken off in the cone end of the vacuum post and needs to be removed. Just bought the truck the other day, 130,000 on the clock and runs like a champ, iot was the guys grandpa's truck,

 

So, Hooked the lines up per the manual diagrams and no love, I am assuming now the job is to check the lines coming off the controller?? or the vacuum block?,I can hear the recirculate door close when i turn the truck off. On the bright side, I was throwing a large leak evap code, the large rubber fitting on top of the charcoal canister was split and loose, so, stuck it back on and ran a zip tie around it, Truck runs even better now that i have that leak under control.

 

Just wanted to add to this thread a bit, it seems the black line that breaks of(where it comes through the firewall at the evaporator opening, is the main vacuum source for the controller, I was getting no vacuum at the controller because the previous owner thought this was for the blend door actuator,(and a vacuum leak as well, I used the factory line for the blend door, snipped the black line at the controller down in the vacuum block area, spliced in some 1/8th rubber line, ran it out the firewall to the left of the steering wheel where a block off was that had my stereo and alarm power wired running through it, up past the brake booster and zip tied it to the wiring harness, routing it over towards the passenger side and spliced it into the vacuum lines there, used a small piece of the old broken line to stick in the nipple and pushed the rubber hose over it. Vents, floor, and defrost all work as they should now.

 

I made my own heater treater with a kobalt 8mm socket. You will need a grinder. I used and 4.5" angle grinder. Indexed the actuator gears and lined up everything per the videos on how to install the heater treater on youtube


and now I have cold and hot air. I also did not cut carpet by using a Milwaukee impact drill bit and a 1/4" wrench and squeezed the bit in-between the carpet. It's tight but worked out great.

 

So OP covers the issue of floor-only air flow at about 2:00 in his video in Post #1.

I recently took a different approach to our beater '98 Ram. First I verified the vacuum actuator for this door was indeed 1) connected and 2) moving. Everything you can see is working as it should but it wasn't moving the flap internally, so broken door basically.

I drilled a ~5\16" hole on the driver side of the HVAC box. You wanna drill below the seam of the clamshell so you don't wind up interfering with the next door in the flow which dictates vent or defrost. Then I crammed some 1/4" round stock in there to push the door open. I went until it stopped, marked it, cut it, welded on a small retention tab and reinstalled permanently with a small sheetmetal screw.

Honestly, it works beautifully and our volunteers can now defrost the windshield or get heat outta the vents on the Colo winter days.

As viewed from driver floorboard looking toward passenger side, I drilled here. Round stock runs wild here (finger indicates)

I was fortunate enough to have a donor with dash already removed. Photo taken from passenger seat area, and finger indicates roughly where I chose to drill

This door dictates vent or defrost but it won't do anything if the "floor door" doesn’t first allow air to get this far. More importantly, you want to place your rod below the clamshell seam so it doesn't interfere with this door

The problematic (in my case) "floor door" lives about here. You can actually see the upper hinge pivot above the green sticker. Since your dash will be installed, youll only be able to see the lower actuating arm tucked between the floor and center bottom of dash

I wound up with a rod ~21.75" but honestly from later measuring my donor 16 to 18" oughtta do it. Mine is going so far it's front of my heater core, which isn't necessary. Anyway my choice of retaining tab shown here

Installed. Works great.

 

WARNING regarding my post above: in hindsight my rod at 21"+ will fight the hot/cold blend door. From measuring my donor i believe ~12.2" is enough to keep the "floor door" open but not enough to interfere with the heat blend.

The joy of trying to rig things to work....sometimes there's a learning curve

 

'Re engineering' other people's crappy engineering - is usually a trial and error process... cool fix.