Air door blend issues

[Raybird2112]

The heat/air blend function on my 06 Liberty is acting weird. On a cold start, it blows hot air on wind shield. After about 20 minutes of driving I am getting little to no air out if my vents. I can switch to different positions but the air direction does not change. The fan is blowing correctly, I can feel the blower is warm, but it is not coming out of the vents. I let the Jeep sit, say overnight, and start it up in the morning and it is working fine again only to act the same way about 20 minutes later.....please offer any ideas. I am flabbergasted?

 

[Billwill]

The vent directions ie. airflow to defroster vents, side vents, footwell etc. are driven by vacuum.

The gassers have a small rubber tube picking vacuum from the intake manifold while the CRDs have the vacuum supplied by a seperate vacuum pump driven by the Serpentine belt.

If this tube is disconnected or has a leak then air only comes from the demister vents.

The heat control is done by stepper motors.

 

[Raybird2112]

The vent directions ie. airflow to defroster vents, side vents, footwell etc. are driven by vacuum.

The gassers have a small rubber tube picking vacuum from the intake manifold while the CRDs have the vacuum supplied by a seperate vacuum pump driven by the Serpentine belt.

If this tube is disconnected or has a leak then air only comes from the demister vents.

The heat control is done by stepper motors.

Thank you for your reply. Much appreciated. Where exactly is the small rubber tube located?

 

[sota]

hilarious: my 07 just had this happen as well.

https://www.jeepkj.com/threads/what-did-you-do-to-your-jeep-today.50782/page-1020#post-772120

did you recently do any work in the dash, where you had to pull the center bezel out?
if you look up under the dash on the driver's side, you can see the two vacuum canisters that run the doors. are they moving when you turn the control knob, with the engine running to create the needed vacuum?

and no, I don't have a definitive answer yet. I need mine to act up again so I can go look at the actuators.

 

[Raybird2112]

hilarious: my 07 just had this happen as well.

https://www.jeepkj.com/threads/what-did-you-do-to-your-jeep-today.50782/page-1020#post-772120

did you recently do any work in the dash, where you had to pull the center bezel out?
if you look up under the dash on the driver's side, you can see the two vacuum canisters that run the doors. are they moving when you turn the control knob, with the engine running to create the needed vacuum?

and no, I don't have a definitive answer yet. I need mine to act up again so I can go look at the actuators.

Yup. I am waiting for mine to act up again to look at the vents. In the meantime, I am going to look behind the center bezel to look for loose connections, etc. Won't have time until the weekend. I'll keep everyone posted.

 

[ltd02]

You can pull the tubes off the controller knob and hook up a little vacuum pump to force the actuators to work.

 

[Squamish_Steffen]

The heat/air blend function on my 06 Liberty is acting weird. On a cold start, it blows hot air on wind shield. After about 20 minutes of driving I am getting little to no air out if my vents. I can switch to different positions but the air direction does not change. The fan is blowing correctly, I can feel the blower is warm, but it is not coming out of the vents. I let the Jeep sit, say overnight, and start it up in the morning and it is working fine again only to act the same way about 20 minutes later.....please offer any ideas. I am flabbergasted?

I have this EXACT same issue.

On startup, it all works; there is lots of airflow and all the settings work for hot or cold, outside or recirc air. After 10-20 min of driving, only 5% of air is coming out of the selected vent, with the rest coming out nowhere inside the cabin. I can hear the blower motor working hard. It sounds like all the air is bottled up inside the glove compartment, as if a blend door had closed on the blower output.

What confuses me most is - regardless of vacuum hoses/actuators - what setting could cause the physical block of all airflow to any vent?? That is not a position I expected the blend doors to have.

 

[Raybird2112]

I have this EXACT same issue.

On startup, it all works; there is lots of airflow and all the settings work for hot or cold, outside or recirc air. After 10-20 min of driving, only 5% of air is coming out of the selected vent, with the rest coming out nowhere inside the cabin. I can hear the blower motor working hard. It sounds like all the air is bottled up inside the glove compartment, as if a blend door had closed on the blower output.

What confuses me most is - regardless of vacuum hoses/actuators - what setting could cause the physical block of all airflow to any vent?? That is not a position I expected the blend doors to have.

I hear ya. It's very frustrating. I don't quite understand it either. I have a bearing going out on the ac compressor, I wonder if this is related to my problem? I'm going to fix the ac clutch and see if they are related.

 

[Raybird2112]

I hear ya. It's very frustrating. I don't quite understand it either. I have a bearing going out on the ac compressor, I wonder if this is related to my problem? I'm going to fix the ac clutch and see if they are related.

I looked at the air blend motors this weekend and all of them seemed to be functioning. I'm going to fix the ac clutch and if the actuators act up again I'm going to text them and see if they move.

 

[jeff b]

I have this EXACT same issue.

On startup, it all works; there is lots of airflow and all the settings work for hot or cold, outside or recirc air. After 10-20 min of driving, only 5% of air is coming out of the selected vent, with the rest coming out nowhere inside the cabin. I can hear the blower motor working hard. It sounds like all the air is bottled up inside the glove compartment, as if a blend door had closed on the blower output.

What confuses me most is - regardless of vacuum hoses/actuators - what setting could cause the physical block of all airflow to any vent?? That is not a position I expected the blend doors to have.

I am experiencing exactly the same issues on my 2005 Liberty. I have removed the heater box from behind the dash and thoroughly inspected the blend doors. I see no issues. I have replaced the blend door actuator as I am told by some that it not only controls the blend of hot & cold air but that it also controls the volume of air expelled through the vents. Upon visual inspection, I can't see how it would control the volume of air. Maybe the blend door actuator somehow communicates with the other 3 actuators that control the directionals (defrost/vent/floor). A mechanic told me that after a little while that the blend door actuator will begin to "drift" impairing the air flow.

 

[sota]

@jeff b if that's the case then I'd think running the control though all the positions should fix it.
It didn't.

I'm at least glad to see i'm not the only one with this problem. I'm concerned that it "cured" itself this time; I prefer broke things to stay broke, so I can fix them.

 

[jeff b]

I am experiencing exactly the same issues on my 2005 Liberty. I have removed the heater box from behind the dash and thoroughly inspected the blend doors. I see no issues. I have replaced the blend door actuator as I am told by some that it not only controls the blend of hot & cold air but that it also controls the volume of air expelled through the vents. Upon visual inspection, I can't see how it would control the volume of air. Maybe the blend door actuator somehow communicates with the other 3 actuators that control the directionals (defrost/vent/floor). A mechanic told me that after a little while that the blend door actuator will begin to "drift" impairing the air flow.

UPDATE>>>I replaced the blend door actuator and I now have good airflow at all times. This was an involved job. It wasn't hard, just time consuming having to remove the dash to access the actuator.

 

[jeff b]

The heat/air blend function on my 06 Liberty is acting weird. On a cold start, it blows hot air on wind shield. After about 20 minutes of driving I am getting little to no air out if my vents. I can switch to different positions but the air direction does not change. The fan is blowing correctly, I can feel the blower is warm, but it is not coming out of the vents. I let the Jeep sit, say overnight, and start it up in the morning and it is working fine again only to act the same way about 20 minutes later.....please offer any ideas. I am flabbergasted?

I had the same problem. I replaced the blend door actuator and now have great airflow.

 

[jeff b]

@jeff b if that's the case then I'd think running the control though all the positions should fix it.
It didn't.

I'm at least glad to see i'm not the only one with this problem. I'm concerned that it "cured" itself this time; I prefer broke things to stay broke, so I can fix them.

I hear ya. It's very frustrating. I don't quite understand it either. I have a bearing going out on the ac compressor, I wonder if this is related to my problem? I'm going to fix the ac clutch and see if they are related.

I had the same problem. I replaced the blend door actuator and now have great airflow.

 

[Squamish_Steffen]

UPDATE>>>I replaced the blend door actuator and I now have good airflow at all times. This was an involved job. It wasn't hard, just time consuming having to remove the dash to access the actuator.

Thanks for the update man! Is the mode of failure more evident now? I'm still wondering exactly what was wrong...

Any chance you can provide a part number or link so we can be clear on the actuator in question? Also, I'm curious if you got to testing the old actuator with a vacuum pump at all? I wonder if vacuum is diminishing while driving, and the old actuator has become sensitive to that. Or it its a direct wear issue with the actuator...

 

[Raybird2112]

UPDATE>>>I replaced the blend door actuator and I now have good airflow at all times. This was an involved job. It wasn't hard, just time consuming having to remove the dash to access the actuator.

How long did this process take? The one behind the glove box?

 

[sota]

It looks like I'm having the same problem. I can reach in and move the blend door actuator, but I'm not getting a change in airflow. I'm still with virtually no air coming out any position, and the blower running a full steam.

 

[sota]

ok I don't know whether or not it's an actual fix, but I this...
https://www.jeepforum.com/forum/f28/blend-door-problem-1469393/#post15152505
jammed a screw driver in there, and I can see it turning when I adjust temperature. I now have air blowing our of any vent I command.
if it farts up again, I'll immediately look to see if the screwdriver turns and report back.
time to make a deposit, then off to more plowing!

 

[sota]

Well it didn't last. Back to having virtually no heat in the cabin. I can see that actuator moving, in fact all three of them move properly. I'm just not getting heat going out the vents like I'm supposed to.

 

[sota]

Are you guys aren't going to believe this one. I think I know what it is. The air conditioning evaporator is frosting over. when I was checking the vacuum line in the engine bay, I noticed that the lines coming off the compressor and off the dryer were completely Frozen over. In fact the dryer was a block of ice. I'm wondering if the coil in the dash isn't completely Frozen over. Test that, I just unplugged the air conditioning compressor. about 5 minutes later I've got full heat again.