HVAC Vacuum Line Routing

01TJ-Blues

01TJ-Blues

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Hey guys. I have read pretty much all of the duct issue posts and think I have identified my issue. Where the line runs across the firewall there is a T than one line enters the cab, the other is routed behind/below the battery. This in my case is NOT connected to anything. Can someone show or explain where this line goes? I have looked and cannot seem to find the culprit.

Any help is appreciated.


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Actually upon more research it seems there may be a vacuum reservoir tucked away in the passenger side fender area. I’ll explore that next.


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Number 8 is the vacuum reservoir.
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The tee connection should split the vacuum line with one going thru the firewall to the HVAC controls and the other as you mentioned to the vacuum reserve canister, the canister need to be connected for your HVAC vacuum system to function properly. Usually most parts places have generic tubing and fittings available so you can replace any damaged components.
 
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TJ4Jim said:
The tee connection should split the vacuum line with one going thru the firewall to the HVAC controls and the other as you mentioned to the vacuum reserve canister, the canister need to be connected for your HVAC vacuum system to function properly. Usually most parts places have generic tubing and fittings available so you can replace any damaged components.
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Yeah,I knew It wasn’t supposed to be just dangling and I looked around to find an empty port and didn’t see anything. Did a little research and found the vacuum reservoir tank was supposed to be in there and it looks like it may have been removed for some silly reason.


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I realize that this is an older thread, but I recently ran into a related HVAC issue and thought that maybe this info could help someone researching a similar issue in the future.

On my '04, fan speeds and temperature could be adjusted, but vent selection was 100% non-functional. I originally thought that the selector knob was actually rotating the selector mechanism, but the doors were stuck on main vents and couldn't be changed. I came here (where I frequently lurk) for assistance and was not disappointed. Using info in this thread I traced all of the vacuum lines, even removing the battery and tray to gain full access to the vacuum reservoir, but did not detect any leaks. I went back to the control knob to check again. Upon removing the knob into better light I noted two cracks in the plastic surrounding the knob's shaft recptacle. Reinstalling the knob, I realized that it was in fact just free-spinning on the selector shaft and not actually repositioning it. After reinstalling the battery and support tray, and a new selector knob (currently $6 to $10 depending where you purchase), my HVAC controls are back in business.

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Good time to check the vacuum check valves and see if your hoses actually even hold vacuum. Those things are skinny & mine were super brittle and broke pretty much just by looking at them.
 
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I'm having the lovely issue of HVAC only working blowing out of Defrost and only when the speed is on high in my son's 97 TJ. When i look at the T where it should go through the Firewall it looks like its disconnected and nothing through the firewall. Any ideas on what it should connect to? I'm digging behind the glovebox and not seeing anything obvious disconnected, hoping it hasn't fallen down where i have to take the whole dash apart. Any ideas of pictures behind the glove box would be helpful. Thanks!
 
The T at the firewall goes to a one way check valve (which you may have in place but may be broken), then t's off under the batter to a vacuum reservoir canister. The other side of the T runs across the firewall into a port near the back of the intake manifold. There is another one way check valve there as well. I had one broken check valve and also discovered that the vacuum line itself is fairly brittle. I replaced all mine. (looks like I may have already said all that in prior posts, sorry).

Through the firewall it becomes the black hose that goes into the connector next to the fusebox behind the dash. Good luck getting to it w/o taking a lot of stuff apart. It's the vacuum supply for the HVAC operation. There's another plug that connects it to the HVAC control. I may have a picture handy...
 
The black hose from the firewall connects to the back side of this. Yours will have the connector plugged in with its hose of many colors that my mama gave to me.

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LattaDad said:
Not what i wanted to hear LOL!

It works just only in defrost vents... I'll have to start yanking dash parts off. Gotta love inheriting this stuff lol.
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You never know what Bubba did before he sold it to you. And no matter how much you check it out before hand, you will never find everything he did.
 
LattaDad said:
Not what i wanted to hear LOL!

It works just only in defrost vents... I'll have to start yanking dash parts off. Gotta love inheriting this stuff lol.
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LattaDad said:
yea my line going into the firewall isn't connected. And i don't see that connection at the Fuse box :/...
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Is the hose back there where the arrow is pointing? Does it go through the hole I circled? It looks as though someone has been in there, the fuse box is unbolted at the top. Is you can find that vacuum connector you can trace the line back toward the firewall or you can just replace a section of the line. If you can find the hose slide a welding rod or antenna through from the outside and attach a section of the nylon hose to the line and splice a new piece into the tee and the piece inside. I use windshield washer hose (3/32” I think) to make the splice. I spray the nylon line with brake cleaner or a dot of super glue will hold the splice together.

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