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ok I've got a new problem. My Airconditioning works in my xj and so does the heat but it only blows out of the defrost vents very lightly... you can only feel it when you put your hand over it. The blower motor works also.. ive taken it out and checked it.. its not the radiator either. I think maybe the problem is that a door inside the cooling/heating ducts is stuck shut a certain way.

Here's the question: Are the duct doors the problem or is it something else
and if it is the duct doors... is there anyway to get in there and fix it?

I live in south Louisiana and summer is here.. so this could be a problem

the blend and selector doors are actuated by vacuum-- verify strong vacuum signal to the doors first-- double check the selector switch has not come loose either- couple of big bumps and it can get disconnected-- don't ask how I found that one out!!!

--Shorty

You, my friend, have a vacuum line leak to your HVAC controls. The vacuum line that operates the air doors runs from your HVAC controls through the firewall just under the pink (heater control valve) line along the passenger side fender and under the battery to the vacuum reservoir (the "black bottle"). when the lines run under the battery tray they tend to corrode, break, split, whatever and a leak will develop there. Trace those lines and if you find a leak, split, etc. fix it (as in repair, not duct tape) and your air/heat will miraculously flow out the front vents.

man I really love this website.. you guys are awesome thanks Ill try it

So, what did you find out? Keep us posted, did you find a split in a vac line?

just getting back from vacation havnt been able to look at it...Im gonna take a look at it today hopefully Ill find the leak

What year is it? It could also be a bad pneumatic valve operator that moves those doors or trash keeping the door from moving. Usually a vacuum leak can be located by the noise it makes.

Here is the info that I gathered from Alldata, I have the same problem:

It was issued in 99 but it may affect yours too..

Heater & A/C - Will Not Switch To Panel Mode

NUMBER: 24-12-99

GROUP: Heating & A/C

DATE: July 2, 1999

SUBJECT:
The Heating and A/C System will not switch to the instrument panel outlet mode.

OVERVIEW:
This bulletin involves installing a panel/demist door vacuum actuator.

MODELS:

1999 (TJ) Wrangler
1999 (XJ) Cherokee

SYMPTOM/CONDITION:

The heating and NC system may not switch to the panel mode. This could be caused by a leaking diaphragm in the panel/demist door vacuum actuator. This symptom could be intermittent and system could switch back and forth from the panel mode while driving.

DIAGNOSIS:

Apply vacuum to the panel/demist door actuator using a hand actuated vacuum pump containing a vacuum gauge. The actuator should hold vacuum indefinitely. If the vacuum bleeds off, the diaphragm is leaking. Perform the Repair Procedure.

PARTS REQUIRED:

1 04864995 Panel/demist Door Vacuum Actuator

REPAIR PROCEDURE:

THIS REPAIR IS COMPATIBLE WITH DAIMLERCHRYSLER'S MOBILE SERVICE PROGRAM AND DOES NOT REQUIRE HOISTS OR OTHER FULL SERVICE FACILITY SPECIAL EQUIPMENT.

1. Disconnect and isolate the negative battery cable.

2. Remove the knee blocker from the instrument panel.

3. Unplug the vacuum line from the actuator (See Figure 1).

4. Insert a trim stick or other suitable wide flat-bladed tool into the actuator mount latch hole to release the latch and gently pry the actuator outwards to remove it from the mount (See Figure 2).

5. Rotate and tilt the actuator to as required to disengage the actuator link from the door lever. Remove the actuator.

6. Install the new actuator, p/n 04864995, by installing the link onto the door lever.

7. Install the actuator onto the mount.

8. Connect the vacuum line.

9. Install the knee blocker.

10. Connect the negative battery cable.

I ended up not being able to really take a look at it today... too buisy. I did get a little time to look at it though. I noticed that a line ... not sure if it was a vacuum line or not.... was disconnect it looked like it was suppose to go somewere on the radiator it ran under the battery.Also I forgot to mention that when I do turn the a/c or heat on and leave it running for awhile it makes a loud screeching noise but it goes away after about 30 sec. year is 96

don't know if vacuum line for storage tank is in same location on '96, but the blend door and selector doors on the older ones opperate off vacuum from a canister that is located under/behind the bumper on the passenger side af the vehicle-- the line runs directly under the battery and could look like it should go to the radiator.

as far as the screaching sound-- sounds like a blower motor starting to go out-- mine's done it for months, but only when it's on "low" setting.
I'd fix the selector door first, then change the blower motor (not too tough to do)

good luck, have fun, and enjoy..... or, at least, good luck!
--Shorty

thanks!

I have a similar vacuum problem.

When the control switch is on recycle, air comes out of the front panel as it should. But under engine load (climbing a hill or accelerating) i.e when there is low engine vacuum, the door closes and no air comes out till i remove my foot from the gas pedal.

I think it could be a valve problem, but which one should i look at?
It's a 1999 XJ