I had an idea that might need quite a bit of fleshing out. I understand there would be inherent risks involved, but I'd like to discuss the merits of 'if it could work' rather than 'if it should be done'. I've used the rear window defroster exactly 0 times so far. My thought was to discover if the lead that goes to the rear-window defroster is a 12v tap from it's control module. And if so, could that 12v be attached to something of equal or lower amperage, such as a fan, to provide air circulation to the rear-facing seats. The added benefit to this would be the following: 1. control from main touchscreen 2. solution to rear ventilation (perhaps even multiple fans if amperage allowed) 3. easily reversible depending on season, but having a subtle switch in the trunk to toggle between the two functions I'm not sure of the conditions that need to be met for the rear-defroster to work. In other words, is there a signal that is sent back to the control module that says the resistance has reached a certain amount, it's time to turn off? Or perhaps a signal that asks "is there really a defroster connected before I turn on?" type of communications. The ideal answer would be that the rear-defroster either stays on until turned off or it stays on for a set amount of time. If I recall correctly, that system is at least 15 amps. Most 12v fans are 3-5amps from what I've seen so far. All it would take is two and they could be positioned for either bringing air further back from the main cabin or blowing directly on the occupants.