More interesting observations about the HVAC UI behavior. Last time it was the Defroster Vent. This time it's the Fresh/Recirculating setting... It appears that even if you disable the "Auto" setting in the control panel, and explicitly set the system for Recirculating air, as seen here: The system will occasionally decide to switch to Fresh Air mode, as seen here: It will switch over for a couple of minutes every so often in some circumstances and then switch back. I assume it's when it detects sufficient humidity in the cabin. I can hear the vent noise change, so it's not just a UI thing. It's not a deal breaker... but I'm not sure shy if you are going to present me with an Auto mode and an option to override it, then why not really allow me to over ride it?