Hey all, this is my first post on here as I've been able to find answers by searching for all the problems I've had so far. So sorry if this is in the wrong section. Anyway I have a 2000 classic XJ and I'm having a problem with the HVAC. I have air blowing through the defrost vents even if I have floor only or top vents only. This is annoying as when I have MAX AC on it tends to fog up the windows as it is allowing air through the defrost vents and top vents at the same time. So if i put it on top vents only or floor only I do get most of the air through those vents but a little bit comes out the defrost vents as well. I have found other post with people have there air stuck blowing through defrost only but not anyone else with defrost and the other vents.
Could it be a blend door/damper problem or maybe my A/C heater controls?
Any help would be appreciated. Thanks.

 

If the air is only blowing out of the defroster you either have a vacuum leak or you blend door isn't operating correctly.

 

OP has defrost together with other vents.
Would still check vacuum lines/connections and blend door operation.

 

where would the vacuum lines responsible be located at? also would the blend door for the vents be located somewhere behinde the center dash? I found the vacuum line that runs by the battery but couldn't figure out where it enters the firewall. By connections you mean behind the hvac controls?

 

Start at the vacuum ball. It is under the front bumper passenger side. Check it for loose hoses and check the ball itself for cracks and fallow the hoses to the fire wall. If I'm not mistaken your year has an electric motor that runs the blend door make sure that is working and moving the door.

 

The Blend-Air Door has nothng to do with your issue. More than likely the defrost door linkage is broken or its actuator is defective.

You can access the defrost door, and its door link, by removing the radio, and other bits.

Here's some photos of a '97 defrost door and broken actuator link.with radio removed.

 

Hmm...I'll defiantly have to check the defrost door and actuator tomorrow when I pull my radio to redo my RCA cables. I'll also check the ball in the bumper and the lines connected to that just to be sure.
BTW CCKen, where exactly was that second picture taken at? Was that further inside/behind the A/C & heater controls?

 

I am also following this. 1999 with same apparent problem.

 

Yes. Inorder to get that far the person that posted that picture on the internet had to remove alot of dash components to get there.

Before going this far, I suggest that you see (hear) if the defrost door is moving.

With your radio removed, isolate all the electrical connectors, place the mode selector on the AC/Heat control panel to position #7 ( Floor door open, Defrost door closed) shown in the pic below, start the engine to charge the HVAC vacuum system, shut the engine down, while listening at the radio opening in the dash, quickly turn the mode selector to OFF (O) and check for a sound of the defrost door opening. Unfortunately the Floor door will move at the same time.

By going to OFF (O), the defrost door actuator will move open because the actuator vacuum is vented and the default position of the actuator is Open.

You may hear the actuator moving but not neccessarily the door moving. This is not a conclusive test so you be subjective here.

I can't visualize blowing the dash apart to get at the defrost door without doing some sort of preliminary testing.

Good luck and let us know what you find out.





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Tried your tip about listening for the actuator and I can only hear one. So I'm not sure if I hear the defrost door opening. After turning to off quickly I hear one move but I don't hear 2 of them. Anyone have maybe a link where someone might have wrote up how to remove the parts of the dash to get to the actuators? I can't seem to find one for my year. I'll i can find is dash removal on a 96 and below. Or is it basically the same?

 

Also forgot to mention CCKen I don't see a flap or door behind the radio and ac/heater controls like in the picture. IDK how to post a pic of what I'm seeing but it looks like there might be one there but covered behind that far back plastic piece.

 

If you want to get at the defrost door I suggest you get a FSM for your XJ. This outfit sells downloads cheap.

http://www.pacificcoastmanuals.com/j...e_manuals.html

Sections 8E and 24 cover most of the disassembly/reassembly steps.

Unfortunately there's no specific steps to repair/replace the defrost door or its linkage while the HVAC unit is still installed in the vehicle.

I've Googled Jeep Cherokee Defrost Door and came up with dozens of hits for the Blend Door but nothing about the defrost door. I did come up with one thread on a WJ site that taked about the defrost door link repair but with no pics.

And, unfortunately I didn't save the forum thread that had those pics I posted. I probably got it from a Jeep forum's DIY subforum somewhere.

 

Well after pulling the dash assembly back on the passenger side, thanks to the FSM CCKen gave me a link for, I checked the defrost actuator. Vacuum lines were on the actuator snug, and the actuator seemed to be functioning correctly as it would open and close the door. But looking at the defrost door there is another opening right beside the defrost door that goes to the defrost vents above the panel vents. For the driver and passenger window. That opening has no door to stop the air flow? My guess is this is where the air is coming from and is also going through the dash defrost vent as there is a gap in the foam that looks like it's to separate the 2. I would post pictures to show the part I'm actually talking about but I'm not sure how to post pictures on here.

 

That small hole next to the defrost outlet is for the defrost duct/demister adaptor.



If there is a breach in the foam between the two outlets it should be rebuilt using bits of foam rubber glued to the existing foam.

Here's a vacuum circuits diagram that shows the various door positions vs. the mode selector functions. Study this diagram and try the various mode selector setting and watch the door actuators on the driver's side of the HVAC Unit. Note that in selection #6, Mix, the defrost door goes to a mid position and the floor outlet door (actuator) opens. You should be able to see the panel door open when #8 or 10 is selected.

 

You may want to do a search for your problem or start your own thread about it. Your post is already burried and is doubtful if it will be answered.