Faint intermittent "chh chh" noise

First of all, has the dealer heard the noise? If so, we need to get it back to them so that they can continue to repair this under warranty.

As for the noise, it does sound like a rotational noise that is pretty consistent.

Does the noise get faster if you speed up the blower motor? The fact that they cleaned it would not repair it in my mind. It should more like a bearing noise which would create the chirping noise. It being dirty would not cause this type of noise so clearly, they returned it without confirming the noise was gone.

https://www.2carpros.com/articles/blower-fan-motor-works-on-high-speed-only

What I would do is if this noise seems to be related to the blower motor, then I would remove it and put it on the bench and test this.

Basically, you can just put 12 volts to the motor, and it will spin and that will tell you if it is the motor because you will hear it clear as day with it on the bench.

That is a hard question without hearing it in person. From the sound of it on the video it does sound like an abnormal noise. However, I doubt the fan will have any issue in functioning its full life span. So, if the noise is heard above normal ambient noises like road noise, radio at a low level, and engine noise then it is something that should be addressed under warranty.

If you have to have everything off except the fan, windows rolled up, and strain to hear it then it can be deemed normal.

What I would suggest is if this noise is there all the time now, just have the tech come out and you show it to them while you are dropping it off. This way they have to acknowledge they heard it and are much more willing to replace the part that is likely causing it.

If it is intermittent, then show them the video of what it is doing so they can at least work off of that.

If they say it is normal and you want to address it, then that is where we will need to access the fan for closer inspection.