Mixer door operation?

Now that I have the 'air box' out of the way to change my heater core, (gee that was fun), I can see my three air mixer doors and watch their movement. It seems to me that the lowest door, for floor heat, does not close all the way when defrost is selected.

Actually, no matter what is selected it moves between half open and full open. What's normal?

Thanks.

Well the defroster door should always be part open.

the defroster door seems happy, moves form full open to full closed depending on what's selected, same with the console vent, full open to full closed, depending on what's selected

it's the floor mixer, stealing at least 50% of the airflow I wonder about

actually I wonder about a lot of things XJ, but this is today's issue

is it safe to close the heater box up? the vacuum controller for the mixers is external

Defrost and heat are usually tied together. If not for that then for the side demisters at the end of the dash (97-01 models).

Bottom line if you haven't noticed any problems before and nothing appears broken then it's fine. The engineers spend a fair amount of time designing the system to do things you might not realize.

What year is it? 1990?

From the service manual.

Panel Position note;

"On vehicles with air conditioning, a portion of the air bleeds through the floor outlets."

Floor Position note;

"The panel door is closed, the floor door is open, and a small amount of air bleeds through the defroster outlets."

Defroster Position note;

"On vehicles with air conditioning, a small amount of air bleeds through the floor outlets.

Wow, I'm not new to bbs use... and yet, I didn't do the very thing I see all the time... yes, my bad, 1990 XJ 'Sport'

hey thanks for taking the time to look into that,

HVAC operation hasn't been as good as it could be so I was looking into other causes while I had it open - if nothing else, so I didn't have to get in there again over the life of the vehicle

but yes, it shifts the air flow pretty well - it just struck me as odd that it left the lower open so far

but, pretty sure it's good to go with the quotes you put up, thanks

If you don't want to go in there again, did you replace the evaporator along with the heater core? I would.

I can't remember the last time I saw an evap fail on the early models unlike the later ones.

I did hear that the later models are notorious. Unfortunately, that's probably why my AC leaks out in about a day (or less).

winterbeater said:

I did hear that the later models are notorious. Unfortunately, that's probably why my AC leaks out in about a day (or less).

Click to expand...

When the evap leaks it should leave oily residue (a/c lubricant oil) on the evap which you should be able to see. Early models the most common leaks in order for the the A/C are the hoses, compressor, line seals, condensor, and finally the evap.

Okay guys, I took one last look with a flashlight, body hanging out the door, neck all bent... and something caught my eye in between the hinge of the heater door and the back of the box...




that would be, an eyeglass arm, three screws, a star washer, one mystery torx head clevis bolt, a gum wrapper, and my favorite, a .22 LR casing jamming the hinge

seems to work better now

Thanks for the update. That is crazy! Sometimes the simplest things are the real problem.

Txakura said:

that would be, an eyeglass arm, three screws, a star washer, one mystery torx head clevis bolt, a gum wrapper, and my favorite, a .22 LR casing jamming the hinge

Click to expand...

LOL funny.

the real problem was the heater core, this was just a bonus - I'm glad I took the time to look into it while I had it all open though

It's funny the stuff that either drops down in the defroster vents or from the dash.

or falls in from the factory - three identical screws and a torx head bolt? wth?

and who in this Jeeps history was shooting a 22 that the casing went down the vent? not sure I want to know about that one

but yeah, there is a narrow gap between the hinge pin and the inside of the case, one of those screw heads was wedged in tight and the heater door may have been binding on it

it works great now, lots of heat and lots of air movement - but getting that heater core airbox out and back in is a major pain, using those studs to hold it is not a very good system

mmm, hijacked my own thread

Txakura said:

or falls in from the factory - three identical screws and a torx head bolt? wth?

and who in this Jeeps history was shooting a 22 that the casing went down the vent? not sure I want to know about that one

but yeah, there is a narrow gap between the hinge pin and the inside of the case, one of those screw heads was wedged in tight and the heater door may have been binding on it

it works great now, lots of heat and lots of air movement - but getting that heater core airbox out and back in is a major pain, using those studs to hold it is not a very good system

mmm, hijacked my own thread

Click to expand...

The other parts didn't look like factory parts to me. Lots of people set stuff on the dash only to have it fall in. The 22 could have been someone shooting next to the vehicle with the window down and a casing flew inside. Glad you found that crap in there.

It's funny for me (nothing against you) because I find doing repairs like that easy but then again I did it for a living and if I wasn't good at doing it I wouldn't have made it in that business. I remember one of the heavyline guys at work saying he didn't like pulling instrument panels. I asked him why since he could rebuild engines/transmissions and he just said because he didn't like it.

my main objection was the idiot box, the box only fits when the studs have found home, but the length of the studs keeps the box out of position - for the box to fit the studs have to be in their holes, but you can't reach the holes because the studs are holding the box in the wrong position - too far back into the lower edge of the upper dashboard

also the bottom stud of the two closest together fell into a stiffening channel in the sheet metal of the firewall, it was almost impossible to get it out of the track it was in to line it up with the hole

If I had to do it again, I would remove the uppermost stud, as the lower two can be seen from underneath, and locate them. The top stud can be replaced with a bolt from the engine side of the firewall. With the fan motor out, alignment can be made reaching through the firewall opening to jockey the box around.

My studs spun, I had to hold them with vise grips on their tips and work the nuts loose. One of them spun completely out of the box. When I had it all out I was able to re-install them before I put it back in. The coarse thread should be easy to find a replacement for.

There are other vehicles I have removed the entire dash boards from, I was not impressed with the design of this particular area. Some of the fasteners were 7mm hex heads, where a straight slot 1/4" would have been a lot easier to deal with,or even, a straight slotted 7mm for that matter.

It just wasn't enjoyable to work on. Nor was it easy. It was annoying working inverted and a general pain in the butt. There was little to no thought behind access or ease of maintenance. You were supposed to buy a new vehicle before the core wore out. It's cheap plastic and bargain basement fasteners to save .$03 during assembly.

If I have to do it again I will use this to fix the problem;

http://www.youtube.com/watch?v=Q3xsMqHu56g

You make it sound as though you didn't remove the dash to take the HVAC housing out?

Sometimes things just don't go right.

the lower dash, center console, passenger kick panel, coolant recovery tank, (had to leave shelf in place for wiring routed through it) and upper dash main bolt as per the manual and another thread here - removed yes

but we should let this thread die, I had added to a heater core thread, but started this one for the mixer doors - the original post was a question of how they cycle, and there was that great stuff you found in the FSM that answered my question

the junk I found may have been binding up the lower door, one screw head was trapped at the hinge, the rest was probably not making a problem yet but along for the ride

the doors seem to be cycling great, the air from the heater door is minimal when defrost is selected, I think its a big improvement and now I know how they should work properly