Thanks for input guys. A few notes back for you.
1. The ESC is clearly a problem---it has to be deleted from system. Fan needs to be either ON or OFF. If there's no way to "trick" the speed controlled motor... an ON/OFF motor needs to go in in place of the speed controlled unit.
2. Duty cycle of fan is "not meant for long periods of time." That's a good point. Obviously changing the fan every so often is not appealing. Whenever the car is running the AC will too meaning the fan too. (I'm in Miami.) What do you suggest will have the greatest durability---metal, plastic, or carbon fiber fan? Am willing to test the duty cycle (by default) but might as well start out with most durable unit.
This unit (below) is 101mm OD which fits planned 4" ducting perfectly. To swap out speed controlled motor for 12v ON/OFF a 40mm motor housing with 8mm shaft is needed. Am guessing at needed RPM being in 15,000 - 20,000 range. Will sort out later if that's too much or too little RPM. If you know of any 12v motor that fits this... please advise.
