Stuck in 4WD and the middle

[sooner_magic]

Yesterday while I was moving the slider control for the Temp on my 91YJ's HVAC it got stuck in the middle so when I try to push it to warm it snaps back to the middle. Can I fix this? Also, when I go offroad I put it in 4H, then when Im at the end of the trail and about to get back on the paved road I put it back into 2H. However, the light doesn't go out. The next day when I start my car the light is still on. If I go from 2H to 4H a few times it the light will go off. WHats happening?
PS If youd rather me not have a 2in1 please tell me. smile.gif Thanks

[grignac79]

The 2H and 4H is related to the Vacuum shifter on the front axle. If the connection leaks you may not be gettting enough vacuum to pull the unit back. Check the vacuum connection at the axel. Hopefully that is all it is.

The HVAC if you look under the dash you can see the cables that control the dampers one on the passenger side and one behind the ash tray. Disconnect them one by one and see which one is jammed and not moving. You may have to do some disassembly. Once done check your cables as they made need some graphite to lube them up so as to actuate smoothly.

[OhioYJ]

The next day when I start my car the light is still on. If I go from 2H to 4H a few times it the light will go off. WHats happening? Kind of sounds like your disconnect unit is jamming up for some reason. Could have a water in the bladder. I'd take the disconnect off and inspect everything inside, and turn it upside down, to let any water that maybe in there drain out.

As for the HVAC, not sure honestly, haven't messed with it enough to really know much about it in a Jeep. Hopefully someone else will chime in.

[sooner_magic]

HVAC: How mch disassembly will this be? Should I take it to my mechanic?
4WD: I have the huge 1991 YJ repair manual. Will this have a diagram so I dont mess up anything, and how hard is this to do? Is there major disassembly? Again, should I leave it to a mechanic? Thanks for the help.

[OhioYJ]

HVAC: How mch disassembly will this be?Don't know for sure, I know there are a few on here that have messed with the YJ HVAC stuff quite a bit, I'd probably give it some time for a few to chime in.

FAQ: Vacuum Disconnect. (http://bbb.quadratec.com/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=38&t=008269#9)
TroubleShooting the Vacuum Disconnect (http://bbb.quadratec.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=38;t=007826).

As for removing it, same post from the FAQ link:

----------------------

Ok I was going to get pictures with the axle, but its dark out and the axle is outside, so here's my best for the moment.

Vaccuum Disconnect 101 :D :

You should see this on the passenger side of the front axle.

http://i6.photobucket.com/albums/y249/mr5oh/vac1.jpg

4 bolts hold it on, I believe it takes a 7/16" socket to remove them. Have a drain pan ready because when you pull this out you will lose a little fluid, shouldn't be very much though. Disconnect the vaccuum line going to the bladder on the right side, also disconnect the electrical connector on the left. Once you get the connector, vaccuum lines, and 4 bolts out, you can simply pull the actuator straight back and off.

Here you can see the "shift fork":

http://i6.photobucket.com/albums/y249/mr5oh/vac2.jpg

Here's what happens:

Inside the axle (you can see this from in the hole were the actuator was, since you should have removed it at this point),

http://i6.photobucket.com/albums/y249/mr5oh/unlocked.gif

The passenger side axle is actually two pieces, when in 2WD drive the wheel will obvisuly turn the right shaft, but the inside shaft on the differential will sit perfectly still.

When you shift into 4WD the actuator uses that shift fork to slide a collar over to lock the shafts together, therefore you have this:

http://i6.photobucket.com/albums/y249/mr5oh/locked.gif

Ok now as for your light, in this picture you can see the other side of that electrical sensor you unplugged, its circled in yellow.

http://i6.photobucket.com/albums/y249/mr5oh/vac3.jpg

When the shift fork slides over it either presses or releases that sensor/switch, which turns your light on and off.

Now, to put your minds at ease, this vaccuum disconnect, comes off as one piece, there is nothing inside the axle, that you can physically remove, or break, or take out, so you will only be removing this one piece. That collar in there will slide back and forth by hand, you have to put the shift fork back on the center of this to reinstall the vaccuum disconnect, but this is very simple, you can clearly see everything, and can position the shift fork by hand.

It comes off as one piece, which cannot be seperated into more pieces, unless you take it farther apart on purpose, nothing will fall out (assuming you have no broken pieces).

http://i6.photobucket.com/albums/y249/mr5oh/vac4.jpg

Next if you take this out, and its destroyed beyond repair, you can do your best to put it back on, or you can even drive without on for short distances (I'd say less than an hour, don't drive it for a week then fix it, and if you do drive it a bunch, check your fluid levels!). You may lose a little fluid, as some will leak out, but not much, so worse comes to worse, you can drive to a shop without it. (You may want to plug the vaccuum lines with a screw or something, just so you don't have a vaccuum leak.)

Anyways, I have a motor that works fine, anyone needs it, send me a PM, first come, first serve. :D

Hope this helps, and gives you a little better understanding, of how this actually works, any questions feel free to ask.

Oh and the gasket may or may not be useable after you remove this. I wouldn't reuse it anyways, my recommendation is to scrap off any old gasket material and/or silicone. Then clean both mating surfaces with brake cleaner, then use Silicone on the vaccuum disconnect, and bolt it back together. I personally use Permatex Ultra Blue (as seen in the pictures). Never leaked on me.

[sooner_magic]

I found the section in the 1991 Service Manual about Heating and Air Conditioning. It has a diagram of the Heating System Components. There appears to be a cable sort of right below/ in front of the heater housing on the pass. side and a cable coming off of where the defroster duct comes out. Are those the two cables you are talking about? I went out and looked under the dash. The one one the pass. side (me sitting in the pass. seat normaly) move most of the way when I push the temp control lever to cool, however when I try to move it to warm it looks like it gets caught half way through. I can push the lever all the way to the right, but when I let go It sanps back to the middle. If you want me to post the diagram I will.

[tonylong]

When you push to the right it's to the VENT position. That should open the outside vent. Check all the way over to the right side to see if something is keeping the vent from opening. The spring is a safety to keep the cable from breaking loose.