That sounds perfectly reasonable. I sincerely thank each of you for going to the trouble. It's especially important because the result will shape how we go about placing the 25 watt resistors that are suitable for upgrading to 12 volts. The original switch will not work over the long run with 12 volt heater motors unless we address the elephant in the room which is the 5 watt resistor that is sufficient for 6 volt but totally insufficient for twice the wattage. 12 volts needs a min of 14 watts.
The 6 volt motor using 12 volt power is still woefully insufficient but if you put the 12-6v reducer in the positive line between the BAT terminal of the switch and the positive power source, you can get away with it.
I am researching this problem on the bench using a test engine to generate the 13.8 volts necessary to really test this issue and the mathematically sound 25 watt power resistors that will reduce the heat to a manageable 175 degrees or less. I have an IR Thermometer to test and report those findings. There is no self evident thought process where the conclusion is expected, rather we just test the system and let the results dictate the solutions.
As it stands, the 6 volt motor using the 13.8 volt charging system that is the heart of our 12v system will bring the temperature to more than 375 degrees on LOW. This is about halved if it were a 6 volt power source which is what the GM engineers expected you would do. Understand the switch is not the issue. The 5 watt quad lead resistor (basically two resistors combined) is way too low of wattage to last with twice the voltage. You can read the data so far and make your own conclusions here:
http://devestechnet.com/Home/Native12VUpgrade#heatersystemI have tons more testing to do, but one thing is certain, that 5 watt resistor isn't going to do the trick for a truck converted to 12 volts. So, where do we put this new resistor array? Since it has to be off board the switch due to size, do we make a small heat sink plate that mounts above the switch using its mounting lug and hide it directly under the dash? Or, do we extend the wires about 3.5 feet and mount those resistors inside the air stream of the heater itself? This is why its so important to know exactly where the switch is mounted. What is in the way?
These are very real issues for 12 volt conversions. The reason people think it's no big deal is because they don't use the switch on LOW very often. The day they do put it on low for more than about 10-15 minutes, then wonder why there is smoke and then no heater is rapidly approaching. Hopefully we can offer a solution soon. Thanks again!
