No air out of vents 1999 LeSabre

[Itchigo]

Hi all, I'm new. I have a 1999 LeSabre that only blows air out of the defroster vents. I replaced the actuator behind the passenger glovebox (really tight to get to). I don't seem to be getting any movement out of it, so I don't know if I have another problem. Is there a vacuum hose that operates this as well? I also replaced the blower on the firewall a few years ago. The center dash display works as if the actuator is working, in other words it shows it's on vent when I'm getting air out of the defrost instead. I'm pretty mechanically inclined, so if you direct me to look at something I can probably handle it on my own.

Edit: After revisiting this a little while ago, I get air from the defroster- always. I seem to be able to turn off the floor vents via the center dash buttons. But nothing out of the vents. There HAS to be a vacuum hose somewhere...

I want to fix the A/C which would require a lot of work, but I don't want to even start until I figure this problem out.

 

[02LTD2.0]

I had this happen on a 1997 Olds 88. Check the vacuum hose at the passenger cowl area on the engine compartment side. I heard a hissing sound and a piece of vacuum tubing actually crumbled between my fingers. I replaced a 2 inch section of hose and had full HVAC functionality again.

HVAC systems will generally default to defrost as a safety feature.

In other words you probably have a vacuum leak.

 

[Itchigo]

I had this happen on a 1997 Olds 88. Check the vacuum hose at the passenger cowl area on the engine compartment side. I heard a hissing sound and a piece of vacuum tubing actually crumbled between my fingers. I replaced a 2 inch section of hose and had full HVAC functionality again.

HVAC systems will generally default to defrost as a safety feature.

In other words you probably have a vacuum leak.

Thanks for the reply.

I had read about this being a problem area so I looked at it. I did repair the vacuum connection under the battery behind the right headlight. The connection went to a small oblong vacuum vessel. No change. What I should have done is check to see if there was vacuum at the hose (I cut out like 10 inches and repaired it).

I also read something about a vacuum connector behind the glovebox that's a potential issue. That'll be my 2nd stop.

 

[02LTD2.0]

Thanks for the reply.

I had read about this being a problem area so I looked at it. I did repair the vacuum connection under the battery behind the right headlight. The connection went to a small oblong vacuum vessel. No change. What I should have done is check to see if there was vacuum at the hose (I cut out like 10 inches and repaired it).

I also read something about a vacuum connector behind the glovebox that's a potential issue. That'll be my 2nd stop.

Look in the conduit of wires by the passenger side of the firewall. I also had a P0171 code at the same time which I solved when I found the crumbling vacuum hose.
Follow the line from the brake booster over to the passenger side. You could spray carb cleaner and listen for a change in engine speed if you find the leak.

 

[02LTD2.0]

YouTube has plenty of videos on how to find vacuum leaks.

 

[Itchigo]

Look in the conduit of wires by the passenger side of the firewall. I also had a P0171 code at the same time which I solved when I found the crumbling vacuum hose.
Follow the line from the brake booster over to the passenger side. You could spray carb cleaner and listen for a change in engine speed if you find the leak.

Thanks for that. Ok, I have a little better idea now. I have vacuum at the rubber hose going to the nylon hose (at the firewall before the Y connector. Now I just have to trace that, and rerun what's bad. I have no vacuum at the plastic container under the battery, so I must have an issue between those 2 points.

 

[imidazol97]

Have you taken off the beauty cover to expose the electrical wires and the rubber hose/ nylon hose? There's a one way valve in it. Hose goes from intake manifold to right side of car through one way valve.
Then the T which sends vac to the reserve tank and inside the car, all in one.
Check for vac at T. Then run car and pull house off at reserve tank. There should be a whoosh as you unplug it after you've turned engine off 15 seconds earlier. Could have cracked plastic tank.
If bac there, then take off beauty cover under passenger dash and remove several screws to remove glove box lid for easy vision.
The black nylon tube comes in next to a-pillar.

 

[Itchigo]

I have vacuum at the one way valve on both ends.

Is the reserve tank the tank under the battery compartment? I don't have vacuum there. I was going to run a bypass to check the line from the one way valve to the tank.

Looks like I'll probably be selling this far sometime in the future. (I got gifted another car and will have too many cars if I keep the new one.)

 

[Itchigo]

Ok, here's the latest.

I have vacuum at the back of the one way valve in front of the passenger firewall. I ran a bypass vacuum line from there to the vacuum reserve tank under the battery. I now have vacuum at the reserve tank, but still no vents. When I tested the old line I blew into the hose and could hear it leaking somewhere around the right shock tower. I ran a whole new line since I didn't want to open everything up to run a new line.

Where do I go from here? Under the dash?

 

[HotZ28]

Yes, under the dash! Do you have vacuum to the programmer? Not mentioned yet, but I assume you have the manual control system, not auto climate control? The thread in the link may help.

Post in thread 'Wiring diagrams, vacuum schematics, and such'

Mar 11, 2023

Sounds like you have a vacuum problem from the engine to the reservoir, or line to the inside. It could also be the programmer vacuum restriction mentioned in the link below. When this change of vent air direction takes place, is the car accelerating like up a hill & then corrects itself under lower acceleration going down the incline. I wish the diagrams shown above had some sort of description as to the item numbers, so you would be able to identify what they are. 🙄

How To Correct Mis-directed Cool Airflow in 1996 GM C & H Cars

• HotZ28

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