Hello...I am new to the forum and have a problem with the defrost/dash output door. I have read almost all of the posts here
about vacuum/4wd/hoses..etc. So far I have replaced the vacuum lines on top of the engine area that I could see. I have replaced
the control head for the AC control. I do have a vacuum at the control head, however it is not real strong. The door seems very hard
to open manually..Is that normal? Is ther a way to test the vacuum pressure at the head control to see it it is in spec?
Has anyone had this problem and had to replace the actuator at the output door? (I am already familiar with removing the dash
for heater core repair, so I have been there...LOL) Thanks in advance. Great info on this forum!

P.S. - 4wd works fine..2-4hi-4lo

 

There isn't much left.
You pretty well ruled out the vacuum system, and the head unit. About the only thing left is some sort of restriction on the door or lever. Maybe a critter died in the way, or a piece of carpet, or maybe it didn't go back together just right during the heater core work. Missing any tools?

 

That's a possibility on the lost tool...Had to use all of em to get the dash out.
I am going back in this weekend and hoped somebody would give some
insight on the vacuum actuator itself. I have an aluminum rod stuck through
the vent to prop the door open right now. Unorthodox, but it is 95+ degrees!
I am going to replace the transfer case vacuum switch too. I will post back
after dash removal # 2 with the results. Thanks.

 

I'd like to see pics. I haven't tackled a dash yet.

 

Here's one of the dash removed. I will try to take some more this time.

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This would be an Excellent time to swap out "heater Cores" seeing how you have 99% of it done already? (Cheap Insurance)

 

Pic is from heater core replacement. I have another problem now with the defrost door not moving.
I will try to take pics of the sequence for future reference. The dash is not too bad to get out, just
tedious work. You just have to be careful and not break anything putting it back in. Helps to have
someone to assist in taking the assembly out and putting it back in. Kinda heavy and awkward for
one person..can be done though. I am guessing there may be tranny fluid in the lines or the
actuator is not working. Going to swap radios while I have it apart.

 

I don't know if this will help or not, but here are some idea of the vacuum hose routing.

It sounds like you might have a mode door out of adjustment or a weak mode door actuator or a control head issue. I don't know if this info helps but here it is
A/C mode is only available on vehicles with the C60 option. When the driver selects the A/C mode, the blower motor and A/C compressor clutch are activated. Vacuum is applied through the red line to the defrost actuator and through the brown line to the mode actuator. Outside air is brought in to be cooled. Air is delivered out the instrument panel outlets with a small amount out the floor outlets.

Panel
When PANEL is selected, air is delivered through the instrument panel outlets with a small amount of air delivered to the floor. Vacuum is applied to the mode actuator through the Brown vacuum line, and to the defrost actuator through the Red vacuum line. The mode actuator will retract, opening the Panel Door. The defroster actuator will retract, closing the Defroster Door and open the Heater Door through mechanical linkage.

Bi--Level
When Bi--Level is selected, air is delivered through the instrument panel outlets and to the floor outlets. Vacuum is applied to the defrost actuator through the Red vacuum line. The defroster actuator will retract, closing the Defroster Door and open the Heater Door through mechanical linkage.

Floor
When Floor is selected, air is delivered to the floor outlets. Vacuum is applied to the mode actuator through the Yellow vacuum line, along with the slave mode actuator through the Gray vacuum line, and to the defrost actuator through the Red vacuum line. The mode actuator will retract, closing the Vent Door. The defroster actuator will retract, closing the Defroster Door and open the Heater Door through mechanical linkage.

Defog
When DEFOG is selected, air is delivered to the windshield outlets and the floor outlets. Vacuum is applied to the mode actuator through the Yellow vacuum line, and to the slave actuator through the Gray vacuum line. The mode actuator will retract, closing the Vent Door.

Maybe this will help with your diagnosis.

 

this is what mine is on a 95 4wd 4.3

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