There are many ways to make your heater work when upgrading to 12 volts, this is just one of them. This How-To describes in detail how to use your Stock Heater Switch with a Heater Assembly that has a 12 Volt Fan Motor. The entire exercise is primarily to have a completely stock looking system, so the new motor looks just like the old motor, the original switch is used. So from the interior or exterior of the truck, you can't tell it has been modified unless you look very closely.
http://devestechnet.com/Home/Native12VUpgrade#heatersystemComments or suggestions appreciated. I have on my To-Do list the bench testing and assembly of a 12 volt system using a 6 volt fan motor and original switch putting the resistor array in the fans air stream so there is something for most everyone.
