No air through vent duct

[AF SSgt]

My 97 lesabre wiil not blow air though the vent duct. It always blows out the windshield defrost duct. Is there an easy fix?

[spinne1]

You probably have a vacuum hose that came off under your hood. Specifically, check the hose running to a black plastic "box" on your firewall right next to your vacuum brake booster.

[AF SSgt]

I could not find any vacume lines off. I should have mentioned it does have climate control.

[imidazol97]

Originally Posted by AF SSgt

My 97 lesabre wiil not blow air though the vent duct. It always blows out the windshield defrost duct. Is there an easy fix?

Does it switch from defrost to heat when you push the heater only button? Do you hear the vacuum motors work when you change to bilevel setting? This is testing to see if you have vacuum coming in the black nylon line through the firewall to the programmer box. You might run the motor for a few seconds to build up vacuum and then turn off the motor but turn the key to ON and push the buttons to llisten. If there is vacuum stored and you have a specific problem, you will hear the switching but the unit won't switch to the AC dash vents.

If you don't hear anything with this test, go under the hood, take off the motor cover by unscrewing the oil opening tube. Look at the back next to the large hose from the brake booster where it goes into the intake manifold. There will be a 1/4 inch black nylon line next to it for the AC. That will go to the area by the metal AC unit in front of the passenger firewall. There is a T and one line goes to the front under the fender in front of the right front wheel. Check that canister andthe connection to it. Sometimes they crack and leak the vacuum.

If that seems okay, run motor briefly and pull off the line at the canister to see if you have any vacuum stored.

Second is if you do have vacuum, you may have the problem with the programmer box vacuum lines inside the car. Under the passenger dash is a box the size of a paperback dictionary. It has 5 vacuum lines connected in a corner through a clear plastic connector and the little black nipples that were molded into deform with heat and age and block the AC lline that pulls the vane closed to stop air from coming out the defrost and make it come out the dash vents instead. Taht line is blue.

You can troubleshoot by pulling off the violet line that connects to the black line coming from the motor and making sure you have vacuum coming in while the motor is running. You can pull off the other lines at the various vacuum motors ont he HVAC unit and see if they get vacuum when the various buttons are set on the AC control unit.

If you decide the line has sucked closed you can take the programmer box off (two screws) and it unsnaps with two clips. Pull out the 5 tube connector and you can snip off the blue line outside and the corresponding line to it inside (different color) and connect the two with aquarium line slipped over both or with 1/8 inch internal diameter gasoline line (free from auto store out of their junk box of small pieces they had cut or left over?) and you're back in business. Or you can replace all connections. A few people have gotten the plastic connector apart and opened it up and reconnected. It deteriorates and glues itself together sometimes.

[Amopower]

This advice helped me pinpoint a disconnected vacuum hose near the firewall, thanks.
Similar topic - when air is supposed to be coming out of the vents, such as Econ or Auto mode, would you expect any air to also come out of the defrost vents? Seems like I am getting some air come out of the defroster vents too, cant recall if that is normal, and I think that more air should be coming out of the vents.

[imidazol97]

Originally Posted by Amopower

This advice helped me pinpoint a disconnected vacuum hose near the firewall, thanks.
Similar topic - when air is supposed to be coming out of the vents, such as Econ or Auto mode, would you expect any air to also come out of the defrost vents? Seems like I am getting some air come out of the defroster vents too, cant recall if that is normal, and I think that more air should be coming out of the vents.

I just noticed we don't live too far apart. I'm in a town outside of Dayton near I70.

There is a bleed of air around the vanes that close off various paths. It usually will vary with the temperature setting, I believe.

But if you've had experience under the dash... go to the leftside of the HVAC box sitting in the middle over the hump. You may have to take off the right side hush panel or maybe just the left with a couple screws on the front edge of the dash and a couple taps holding it against the firewall. Then above the accelerator pedal you'll see the vacuum diaphragms that pull the doors when vacuum is applied. You can push on the back sides against the diaphragm because the backs are partially open--not covered by plastic. Look for one that rotates an axle that is horizontal and parallel to the firewall. That vane closes off the flow to the defrost vents and makes any air going up the stack go out the front vents for AC. Apply vacuum by running the motor and the heater set on dash vent. Then put your fingers on the back and push in a little more to see if there's more movement. Of you can do this manually.

If it doesn't move far enough it could be binding or the vacuum amount may be low or a tear in the diaphragm rubber may be lowering the effective vacuum pull on the diaphragm.

A note. The typical problem is that the programmer box on dual systems has a connector for the plastic vacuum lines in the corner of the box. The connector has little thin layers of rubber that suck closed over the vacuum and keep it from getting to the lines and the vacuum motors. The dash vents is usually the first to deteriorate and not apply correctly.

The fix is to replace the connector with a piece of 1/8 inch internal diameter rubber gas line hose (free from scrap bin at auto parts store?) or a size of aquarium line to connect the inside line and outside line on the connector. You could do this for just one or for all 5? (I think there are 5).

http://i86.photobucket.com/albums/k1...7/DSC03124.jpg

This is the connector showing the tubes on both sides. Note they are different colors. The transparent plastic can be separated from the black and ream the openings and then reassemble. But it may not seal--use silicone. I just cut it out. It's hard to get apart.

If you have the single control system yours will be different.

You can switch a vacuum line from one of the other motors to the AC/defrost motor and change settings on the controls and see if it will apply properly with one of the other lines--or connect a line directly from somewhere on the motor such as the place you found one off on the firewall storage tank.

[brcidd]

Well what do you know--small world- Imidaz-- I too, live outside a small town north of Dayton - Troy- and work in Vandalia.....what town are you in-- Huber Heights???

[big white bufflo]

it could be the mixing motor behind the glove box they go bad and cause the same issue it may blowe cold air out the defrost and warm out the bottom its some time intermitten if you turn the key off some time it reset it self and work fine then the trouble comes back only way to see if it woking is to watch it look for your climmate control module it on top of that it a little motor that run the vents

[imidazol97]

Originally Posted by big white bufflo

it could be the mixing motor behind the glove box they go bad and cause the same issue it may blowe cold air out the defrost and warm out the bottom its some time intermitten if you turn the key off some time it reset it self and work fine then the trouble comes back only way to see if it woking is to watch it look for your climmate control module it on top of that it a little motor that run the vents

The actuator on a dual system controls the temp blend door to the driver. It's on top of the box. The defroster is a vacuum motor on the driver's side of the stack.

If a dual system the passenger blend door is controlled from the programmer box with a motor inside and a link rod.

His problem is vacuum and the easiest is a 10 foot piece of small tubing from the vacuum port on the motor or the reservoir on the firewall and apply to the vacuum motor inside to see if it works -- or buy a hand vacuum pump for testing.