Question about air from HVAC vents on earlier model TJ

TJRick

TJRick

TJ Enthusiast
Joined
Oct 2, 2019
Messages
414
Location
South Carolina
When the HVAC selector is in the VENT mode, should *all* of the air flow come out of the front vents only?

I have a 1998 Jeep Wrangler that has the earlier style "slider" HVAC controls with A/C. Whenever I move the upper slider to the VENT or A/C function and turn the fan up, I hear the blower blowing hard, but I get about the same amount of air from the defrost vents as I do from the front dash vents. Is that normal?

This is the airflow I get through the different functions:

VENT:
air blows through the front dash vents, and about the same amount of air blows through the defrost vents and the floor vents. (Is that normal?)

FLOOR:
air blows primarily through the floor vents, and a little less also blows through the demisters.

FLOOR/DEFROST:
air blows primarily through the floor vents, and about the same amount blows *cold* air through the demisters.

DEFROST:
air blows through the defrost vents ONLY.
 
Can someone drive their Jeep and select the VENT function on their HVAC panel and tell me if the air is only coming out of the front dash vents, or if it is also coming from the defrost and floor vents?

I would really appreciate it.
 
I seem to remember something about older model TJ's having a different style system for opening/closing the blend doors which I believe are what adjust the air flow out of different vents. You may have to wait for someone with your specific model year to weigh in.

I'm not experienced with this system at all but it sounds like stuck blend doors maybe? If air is coming out the way you describe on different settings.
 
I've never owned an earlier model TJ, so I can't comment. Hopefully someone will chime in here. I'll keep bumping this thread until someone sees it.
 
In the vent face mode. Center and side dash vents

In the vent feet mode I get feet and defrost vents

I hope that helps

20200302_161954.jpg
 
Thanks, Chief!

Okay, then that means that something is obviously wrong with mine. I looked under the dash while I went through the functions, and I watched all of the different doors open and close, and I don't see a problem there.

Does anyone have any ideas?
 
On both my 97s, dirt or something gets gunked up in there. I also had a blend door break inside so it looked like it was working but inside wasn't moving. Overall poor design not intended for longevity
 
I have a '98. It seems like it usually takes about 10 minutes for it to start blowing properly, from the "face" vent.
Like it blows from everything else, then decides when it wants to, to do what the lever says.
 
When you look at the vacuume cylinders that control the doors and they look like they are working ,if you put the setting on defrost and nothing comes out the arm inside is snapped. I just fixed mine the other day. Very easy..the very top lever works the defrost. Part number 17910.01. Not 02 like I was told and couldn't figure out why it wasn't working. The shaft on the .01 is longer than the .02. I installed the .01 in minutes..DONE. haven't had defrost mode for three years. I was sticking a hangar in the top vent to hold the door open lol..
 
bigwheel53 said:
When you look at the vacuume cylinders that control the doors and they look like they are working ,if you put the setting on defrost and nothing comes out the arm inside is snapped. I just fixed mine the other day. Very easy..the very top lever works the defrost. Part number 17910.01. Not 02 like I was told and couldn't figure out why it wasn't working. The shaft on the .01 is longer than the .02. I installed the .01 in minutes..DONE. haven't had defrost mode for three years. I was sticking a hangar in the top vent to hold the door open lol..
Click to expand...

Thanks, but my question was whether or not air should blow out of the defroster and floor vents whenever the VENT or A/C functions are selected. Mine seems to split the air flow between the dash vents, defroster vents, and floor vents.

I went and looked under my dashboard again today, and watched the actuators move as I went through the functions. All of the arms moved, as did the black plastic levers. Interestingly, it seems like it was designed this way?

When I select DEFROST, the arm moves the actuator all the way open so that all of the air is directed to the defroster vents. But if I select VENT or the A/C functions, that same actuator closes partially, while the vent and floor actuators open, splitting the airflow to all three locations. The defrost and floor actuators *will* close completely when I select the other functions, so they aren't broken.
 
  • Like
Reactions: Paparock1
TJRick said:
Thanks, but my question was whether or not air should blow out of the defroster and floor vents whenever the VENT or A/C functions are selected. Mine seems to split the air flow between the dash vents, defroster vents, and floor vents.

I went and looked under my dashboard again today, and watched the actuators move as I went through the functions. All of the arms moved, as did the black plastic levers. Interestingly, it seems like it was designed this way?

When I select DEFROST, the arm moves the actuator all the way open so that all of the air is directed to the defroster vents. But if I select VENT or the A/C functions, that same actuator closes partially, while the vent and floor actuators open, splitting the airflow to all three locations. The defrost and floor actuators *will* close completely when I select the other functions, so they aren't broken.
Click to expand...
I hear you. Somethings not right in there. Could be a problem with your heater control panel that's sending vacuum where it shouldn't be. sounds like its not splitting where the vacuum should go. Sound logical?? If you look up part number 17910.02 or .01 you will see how the lever controls the doors.
 
Hey guys - I have another question along these lines. For the two AC functions on a 97/98 slide controls, does it (should it) blow air through the upper vents and floor vents or just upper vents?
 
I actually have another question here. How do I reopen my vents? I have a 98 tj that was in the shop for a few days but they said that they did not mess with it.
 
Meghanhue22 said:
I actually have another question here. How do I reopen my vents? I have a 98 tj that was in the shop for a few days but they said that they did not mess with it.
Click to expand...
Also, the air/ heat is coming out but only out of my defrosters. Not my floor vents or the front facing ones. I’m not sure how to fix it
 
It sounds like the little plastic tip that connects to the vacuum actuator broke off so nothing engages when the vacuum signal changes. There are some good write ups on this if you search it
 
Meghanhue22 said:
Also, the air/ heat is coming out but only out of my defrosters. Not my floor vents or the front facing ones. I’m not sure how to fix it
Click to expand...

The defroster vents are the default position. So that tells me that you probably have a vacuum issue.

There is a vacuum hose under the hood that can crack or come off, rendering the HVAC useless except for the defroster vents. Crawl under your Jeep and look under the passenger side, underneath the battery tray. You will see a vacuum reservoir with a 45 degree tee sticking out of it that connects to a hard line and then goes on to the intake manifold. Make sure it is connected and not cracked.
 
Top Bottom
Back