The fan has electronics in them to adjust the speed and turn them on and off. I bought 2 of these and installed them, they are junk. Because the the motor is mounted backwards the fans rotation is reversed and when the cabin gets hot with the fans on high the blade spins off into the fan cage (bad design) The wires do have polarity and you can't reverse them because of the electronic switch. The good side is they are very quiet, but I think that is because they hardly move any air. I took both of mine back and got different ones that work. I think the company is going to be hating these because of all the returns.