I am going to attach pdf file with detailed explanation and diagrams showing/explaining air heat and defrost paths. I've been having fogged windows after heavy rain. It seems I've never used full defrost mode before. 9 page pdf has diagram (last two pages) of complete system. Forget the first 7 pages. Just go to the last two pages for very detailed diagram. It will take an hour to fully digest material but you will always know how it all works hereafter.
Ok, I'll bite. How do you define "full defrost mode"? I'm guessing I would get maximum fog clearing by toggling the front defrost button on (which also turns recirculation off) and raising outlet air temperature to the max. Rear window fogging has never been a problem in our car, so I rarely toggle that switch on, but is there any benefit from turning it on as well? I prefer not to use the front defroster all the time in the winter because heating outside air requires more running time for the ICE. Most of the time I use recirc and only turn on the front defroster when fog on the windshield and side windows becomes very noticeable. Usually letting the front defrost run for a minute or 2 clears the fogging sufficiently that I can go back to recirc for another 5 or 10 minutes. Is there a better way to save gas and keep the windows clear? Edit: I should mention that I'm talking about the HVAC system on our Gen 2 car, not the Gen 4.
