ronandsue74 Report post Posted April 7, 2016 I have a Cat C-9 engine in my 2005 CC inspire. Since I had my leaking aluminum radiator changed three years ago to a steel & copper radiator my fan isn't running fast enough in low speed to maintain a constant 200 to 205 temperature. The engine temp will climb up to 206 the fan switches to high and runs until the temperature reaches 190 degrees. This cycle continues constantly regardless of the ambient temperature or weather or not I'm climbing a grade. What I would like to do is increase the fan's low speed rpm enough to maintain a constant temperature when not climbing grades or driving in high outside temperatures. I have a Sauer Danfoss fan controller #1090385 my controller inputs are from the ECM. My fan defaults to high speed whenever power is not present to the controller. That being the case, can I simply add an in line resistor to the 12 volt power going to the hydraulic control valve. My logic is if I can lower the voltage going to the hydraulic control valve, a little, that in turn will allow the valve to close a little more allowing more hydraulic fluid to the fan motor. Does my logic sound plausible? Any compelling reason why I shouldn't try to add a resistor to the 12 volt power supply line going to the hydraulic control valve? RJ 2005 CC Inspire #51264 Share this post Link to post Share on other sites
wolfe10 Report post Posted April 7, 2016 Ron, There may be a simple answer, but I would do nothing until consulting with both Caterpillar AND Sauer-Danfross. Ideally, you do want a 7-10 degree "window" between thermostatic controlled temperature and high fan speed. Agree 190 to 206 is a little much. Share this post Link to post Share on other sites
