Climate Airflow with 'Fan Off'

[ATwoZ]

So I'm trying to determine if this is normal (guessing it's not), and what might be going on.

So on a roadtrip recently I noticed I kept getting cold air coming through the vents regardless of temperature set. Even pressing 'Fan Off' I was still getting airflow from the vents. As I started playing around more I found the difference based on the 'recirc' option. If the climate controls were not set to recirculate (pull outside air) it seems like air would flow in from the outside regardless of any climate settings, so even with Fan Off etc I would still get airflow in.

As soon as I switched the recirculate option to 'recirculate' I can control airflow and there is no extra air. Turning the Fan Off does exactly that and turns off airflow.

Does this sound right to folks? If not, what should I check?

 

[Sandroad]

Here 2 ideas. First, check to see if the recirc/fresh blend door mechanism is broken. Open the access doors behind the glove box and see if the blend door operates smoothly and completely when you hit the recirc button on the dash. Many are broken by ignorantly forcing the blend door open when the system is not in recirc. If the blend door doesn’t work, odd things can happen with airflow. Second, there is a TSB for strange airflow due to servo malfunction.

https://static.nhtsa.gov/odi/tsbs/2021/MC-10187278-9999.pdf

 

[MikeVpdx503]

I believe it is normal to get fresh air blowing in with fan off and you are in motion, unless you select recirculate. When recirculate is not selected and the fan is off, you are getting airflow from the front intake running through the system. When driving, it is forcing the air through, when stopped, you should not be getting any airflow. Not sure if this would explain why you are getting cold air though, since mine blows whatever the outside air temp when fan is off. My recirculate door is functioning correctly (it was fixed in the past) and what you describe basically the same as how mine functions.

 

[bloc]

Did this still happen when stationary?

With fresh air on, it is plausible that movement down the highway is causing low pressure behind the rear tires where the cabin exhaust air vents are closed pulling air through the AC system. Then, if your cool box is on, the

 

[LTSR]

Here 2 ideas. First, check to see if the recirc/fresh blend door mechanism is broken. Open the access doors behind the glove box and see if the blend door operates smoothly and completely when you hit the recirc button on the dash. Many are broken by ignorantly forcing the blend door open when the system is not in recirc. If the blend door doesn’t work, odd things can happen with airflow. Second, there is a TSB for strange airflow due to servo malfunction.

https://static.nhtsa.gov/odi/tsbs/2021/MC-10187278-9999.pdf

just to piggy back off of @Sandroad - this TSB applies all the way to 2019 models:

https://static.nhtsa.gov/odi/tsbs/2020/MC-10176693-9999.pdf