Scotty, I have a question with modern car heating and A/C systems. So I live in PA where I usually run the heat this time of year in my car and usually only run the A/C between April and October. When I run the heat this time of year in my car I usually use the floor vents only if the windshield doesn't need to be de-fogged, or if it needs to be de-fogged, then either floor and defrost, or front defrost only. In my current car (2019 corolla), heat works great, but I notice that when I have the heat on floor only, later on when the car warms up from the heat running, occasionally it will automatically switch to bi-level blower setting (floor and dash vents). A few times I have used the bi-level setting for sometime, and have had no problems or anything. Although My parents years ago back in the early 2000's or so told me that using the bi-level (floor and dash) is not very good to use for the heat or even A/C for some reason. I believe they said it can damage the heating system if that setting is used often or something like that. Is that true today with modern cars like my corolla? Or was that only true for older cars from the 90's and before that? Or maybe it was never true?
Since my parents told me that years ago, in the previous cars I've driven (early 2000's vehicles) I've never really used the bi-level setting for the heat.. I also never use the bi-level for the A/C in the summer since I always like it blowing on the dash only.
Let me know about this with modern cars heating and A/C systems.