3rdpig

Hi, I've got a 98 ZJ, 4.0, Limited with the climate control A/C. Recently, on it's own, it switched from the dash vents to the floor and defrost vents and won't switch back. I've done the diagnostic self check on the climate control and it comes back 00 with no fault codes. it's 114 degrees at the moment and all I really want to do is get that door moved to the dash vent position, later in the year I'll fix it properly. Does anyone know which motor controls it and where it's located? I searched but every answer I get is for the vacuum operated system, which I don't have. Thanks!

wingless

Welcome to the forum.

There is a black vacuum hose poking through the center of the firewall, to provide vacuum from the engine to the HVAC system.

The symptoms indicate that vacuum connection no longer exist.

A common problem is the hose having broken off at the firewall.

Has that been examined? Results?

3rdpig

Mine is the electronic, climate control A/C, I do not believe there are any vacuum hoses going to it, and I've searched and can't find any, but I will look again. When I pull the control unit out there are only electrical wires going to it.

wingless

This topic shows that potentially problematic vacuum hose on ZJ vehicles w/ manual controls. Mine is manual / vacuum.

The FSM says that the Heat / Defrost Panel / Defrost door motor is electric, not vacuum in the ATC ZJ vehicles.

FSM section 24 has extensive operational / diagnostic info. The FSM is a good place to start.

This is 100% not fun, after personally having disassembled the dash on my ZJ to replace the evaporator.

Good luck.

3rdpig

I've got a Limited with the electronic temp control, I'll put a picture of the dash unit below. I can't find the vacuum lines anywhere that are in the thread you linked, so I'm thinking my ZJ is fully electric/electronic. I'm 6'4" and 230, so getting my head and shoulders in a position to see and manipulate the levers under the dash is just not possible, so I put an inspection camera up there (pic also included) and watched as I moved the controls and the mechanism doesn't move at all when the dash controls are changed and I know they used to when it worked right. Fun fact, our other car, a 2003 DeVille, has a similar problem in that it only blows cold out of the passenger vents. When when that started a few weeks ago I thought, "The A/C in the Jeep works great, we'll just drive that until summer is over!". lol, a great plan.

I checked out the section of the FSM you referenced and did find a lot of valuable diagnostics that can be run from the panel. As soon as it the sun is down I'll go out and try it. I'm not sure what good it will do me, but maybe it will help pinpoint what part is bad. I'll update this post with my results.

Thanks!

3rdpig

Well, I ran all the tests, even the ones that don't apply to my problem, and according to the diagnostic display everything works fine. The Mode Door diagnostic shows a code for what position it's trying to move to and a code for when it's in position, and that all shows that it's working correctly, but again I get no change in air flow. I had the inspection camera in place during the test looking at the door actuating levers and there was no movement, not even the slightest bit, from those levers during the test or the reinitialization of the system.

So I have to assume that the control unit is fine and the fault is in the wiring or the motor. And since the A/C does work it's going to have to wait until outside temps are below 90 before I'm going to feel like doing it. The FSM doesn't make it seem all that hard to replace. But another problem I'm having is I can't find it for sale, everyone has the blend door motor, but I've yet to find the mode door motor.

I'll update this thread, assuming it's still here and I can find it, when I have it apart and have pinpointed the problem.

Thanks for your help!

wingless

YW

FWIW, hands down, the absolute hardest job on my total ZJ rebuild was removal and replacement of the HVAC system, because of the total dash disassembly required.

Good luck.

Cherryokee

Maybe I'm mis-interpreting what I'm looking at but...

When viewing the under-dash images, at the white plastic linkages, there's a silver pin and armature that appears out of position as-if detached/dislodged from what looks like a corresponding linkage pin hole. Can you see it? Can you manipulate it into the hole?