The cabin heater fans have three wires each. Black, red, white. the manual says you don't use the white. I have a switch that has "high off low". That is the same switch that McBean uses. I want both fans to run at the same time and at the same speed but I want a high fan speed and a low fan speed. Can anyone enlighten me? How is this achievable with only two wires from each fan motor? I am wondering if I achieve it by having the vertical power box push out slightly more power when I switch to high. I have a huge learning curve to tackle when it comes to this electrical stuff.