HVAC air flow problems

[davidmiller59]

Hello,

I have a 1999 Jeep Grand Cherokee.
I replaced the blender doors in the HVAC behind the glove box.
Turning the fan on, the air only comes out the front registers. Great for AC, but that's about it. When I move the control to blow the defrost or the floor, it doesn't work. It keeps coming out the front registers. My recirculation door is okay and functions good.
I can't see a vac line off anywhere under the hood, although I haven't checked under the front headlight yet. From reading other posts, apparently a common problem with the "under the headlight connection" causes the defrost only to work. I have a different problem here.
Any ideas?

 

[superj]

are there any vacuum lines under the dash that have to do with that?

 

[JPNinPA]

What rpm do you idle at?
You could spray around for the leak. Don't forget the vac reservoir under the battery


JPNinPA
Using Jeepz.com app

 

[k-2]

this is STANDARD or manual HVAC controls, no LED's type BS. Pict 1 manual is this correct?


The issue is "MODE" doors. not switching - they are vacuum controlled, maybe yu unplugged a line
see pict 2 actuators

GTG I will look for vac diagram - I see no reason to suspect vac reservoir under hood.

 

[davidmiller59]

That diagram helps a lot. It must be an actuator or vacuum problem. Where is this actuator located. Is it easy access?

 

[superj]

probably not. but it should be somewhere behind the radio or glove box

 

[k-2]

look by gas pedal -
did all operate before your repair?
did you move any vac lines?


FYI defrost is the default position no vacuum applied as in loss of vacuum.

PS this is MANUAL control picture #1 above?

 

[davidmiller59]

It didn't work before the repair on the blender doors. It was like it when I got the vehicle. Defrost being the default position without vacuum, means vacuum isn't a problem. All air comes out the front vents no matter which setting is selected. I'm going to look for the actuator today and check it out.

 

[k-2]

sorry busy day for me - no time to solve this.... Attached dia looks like 1/2 half a puzzle but info is there
mybe vac lines swapped

I think the mode doors are incorrectly set up.


Is that your HVAC controller in dia above?

 

[davidmiller59]

Following up on the inspection of the actuator by the gas pedal... I took a look in there and the actuator is detached, most of the rod linkages are missing...haywire tied around the cams. No wonder the HVAC air flow is messed up! Repairing this is going to be a significant challenge. Looks like the entire dash has to come off to get at the linkage. Forty years of wrenching in the backyard and never taken a dash apart. Not sure how to do it...maybe I'll have to hire a mechanic unless I can get a good DIY video or something.
Thank you for posting all this great information. It helped me a lot and its not over yet.
Cheers!
David Miller