Air (hot and cold) stop working on long drive

[mc288]

Hey all,

I have a 2009 Lucerne that I have been taking care of for a while. This site has been a ton of help so far, but this issue is one that I cant seem to figure out.

On long drives (1.5 hr+) I usually set the temp to 72 F and set it to auto. What has been happening is that after a while I realize the car is starting to get warmer so I turn the blower up but no air is coming out. This happens on both the driver and passenger vents. I can hear the blower speed up, and I can feel the air "trying" to come out, but it feels like it is blocked by something inbetween the blower and the vents. I saw some information referencing the blend door actuators, but I pulled over one time while this was happening and I could verify that they were moving. (I removed the glovebox so I could observe on long drives).

If I switch between AC and Heat I can feel the air change temperature, but it is still only leaking out of the vents. If I change between fresh and internal air there is no change. I have not noticed a change if I have the passenger control enabled. Every manual and post I have seen only seems to reference the blend actuator, the actuator for defrost/feet/normal, and the fresh/recirculation. As far as I can tell it is none of these, but it is tough to diagnose since this only happens when I am on a long drive so I cant exactly get my tools out and start looking.

In normal operation it does seem that the driver vents have slightly lower pressure than the passenger, but nothing significant. If I shut the air off for 15-30 min and then turn it back on sometimes it will work after this.

Hopefully someone has seen something like this before because I am lost.

 

[2007LucerneCXL]

If not a actuator it could be the control unit as being a CX it's not a dual temperature setting unit. I'm not sure on how to check the control unit other than switching between functions and seeing if there is a change.

Here's the diagrams, you may have already seen them, but there are a number of actuators that will effect airflow. As a possible problem is the external air temperature sensor, but that should be something to confirm on the dash readout.

 

[mc288]

Thanks, I had not seen that exact diagram before. I haven't noticed anything with the external sensor, but I will pay attention. I'll have to make sure I know where to look for each of these components and hopefully when it happens again I can see if it is one of them not working.

 

[2007LucerneCXL]

Other than using a professional shop tech tool it's pretty much hands on visual inspection in a area that has little room to move or see. I've used a inexpensive endoscope, Ebay - Amazon, that plugs into a phone or tablet which has saved me from visiting the chiropractor trying to see items that weren't meant to be seen lol.

 

[MelsRegal]

Instead of touching the fan speed, which on my Regal disables Auto, lower the temperature and see what happens.

 

[mc288]

Instead of touching the fan speed, which on my Regal disables Auto, lower the temperature and see what happens.

I have tried changing the temperature from min to max hoping that if something was stuck that the sharp changes would break it free, but that does not seem to be the case. I can feel the air leaking out changing temperature but there is still something blocking it.