Heater Motor Controller/Thermister

I have a 1954 IH R-110 and I am trying to get the heater motor to run properly. I am running my system at 12V and I am sure it is a 6V motor but I have found a converter for that. I also found a new 12V heater switch but there is a device in series with the heater switch that appears to be a thermistor that helps control fan speed. I have done some testing and it appears that the fan speed is best at 1V, 1.5V and 2.0V. (My new switch had 3 settings.) Does anyone know what I am referring too? And if so, is there a good work around? The old truck cab is getting pretty cold on those Sunday rides these days.

some pictures would help. Without know what switch and motor you used, it is hard to help much.

Sounds like a simple resistor. Some switches had ceramic resistors built into them, eliminating the need for a separate blower motor resistor.

A Happy New Years Greeting to everyone! One of the many IHC "projects" that I have going now is my heater resurrection. The heater I have is the double barn door type that reverses the motor direction, cw gives you heat, ccw gives your defrost. I purchased the two speed push/pull switch that Buzzman suggested( thank you) in my Dec. 23rd post and have a reversible motor on order from http://www.surpluscenter.com. This motor will need to be modified to fit in my housing( like everything else that I have done on this truck), but after talking to their tech support people I think it will work. No part number is given because I bought the last two they have, although there are very many others on the web site that could be made to work. From my research i found other Non reversible motors that should also work( note: these are grounded thru the case, I didn't want to isolate them to deal with reversing the rotation)....
Oreilly p/n's:
35511- 12v
35512-6v
I'm still working on the off center fan hole issue caused by the DPO( dreaded previous owner), at this point wishing I lived in Canada closer to Nick and his work shop......
I hope this helps...
Terrell
Columbia, Mo
PS: If this motor thing works as I hope, I will be selling the second motor with the other 15 years of accumulated of IHC parts and pieces to get out of my storage unit this summer.....at least that the plan that I have told my bookkeeper(wife)! We will see.