Wife was driving kids to school and called me in a panic that there was smoke coming from the front of the hood (near grill). Car drove fine, but her and the kids smelled a strong burning rubber smell. I told her to shut off AC/heat and come home. She said it stopped. I then drove it to work and did not see it (even after turning ac and heat on and alternating between the two). I had smelled the rubber smell a few weeks back, but did not see smoke. She took a picture of the smoke but I don't see a way to attach it to this post. They did just run heater this morning. 12v battery looked fine. I did not see any burn marks on any hoses (that I could see).
Switching to heat does cause a bunch of racket to emit from dash. Sounds like rodent running through dash (it's not). Fairly loud cracking/popping, and gurgling sounds. I guess the baffles have to switch when it kicks on, but I would not expect that much noise and would not expect it emanate from the full width of dash.
So, are there any belts in the front of car? where are the heating coils? could there been something (debris) that had to burn off after not using heater for some time?