Burning smell out of vents.

[NOV87]

Hello,
I have had a couple of occasions of burning smell coming out of interior vents.
First time I noticed it a couple of weeks ago. Cruising on a HWY, fan is on second setting, temp dial right in between blue and red. AC is on. Noticed that, momentarily, warm air out of vents became cold and started smelling like burnt brakes. At that point, I turned the AC off and moved the temperature dial up and down. The smell slowly went away and the warm air came back, but I could not duplicate the issue, no matter what I did. Tried turning the AC on and off as well.
Thought to myself, that maybe there was a vehicle somewhere in front of me driving with parking brake on. There was no wind, so that was theoretically possible.
Today, I was driving home and experienced the same smell again. The same type of driving and the same
setup of temperature dial, fan speed dial and AC. After, I got home, popped the hood open and looked around. Could not see anything obvious. Not sure what to think of it.
The truck is 2014 HEMI with 33k. Purchased 3 months ago. No other issues noticed. Also, for what it's worth, two months ago, I did cabin filter mod. Don't think, it has anything to do with it, though. Will try recirculating air, to see if that can help determine whether it's coming from outside or from the cabin
Any ideas, suggestions would be greatly appreciated.

 

[SJGUSMC21]

Did you ever figure it out? Same happened to me yesterday. Was driving my daughter to her French Horn lesson, turned on the AC.....burnt 'brake' smell coming thru middle vents as well as some smoke. Quickly turned off the AC....put the heat back on, and all was well. Tried to duplicate it, but it did not happen again. Under the hood, all looks well. I was thinking maybe the air compressor is randomly freezing up? IDK, I am certainly no mechanic, but I try. 2014 Ram 1500 LS 3.6 Pent. 106K miles