4th Generation Dodge Caravan has issue with rear fan not running from front control or the center control. Where should I start testing to make sure there is not a broken wire to the back control and fan? I have done as much testing(fuses, relays, wiring/voltage to the switch with only voltage to switch but where does it go from there to get to the overhead switch and then back to the fan. How do you test the switch so you know if it is passing throught the switch right.