2007 C230 V-6 120k miles: radiator fan appears to come on while driving or idling when it doesn't seem necessary. The fan may pulse at times, run for 5 seconds then go off. I did not notice this during the hotter summer months (Texas) when it rarely came on at all. Temp gauge remains steady at these times. Antifreeze has been changed every two years and still is very green. The coolant system does not lose coolant, no leaks either. Doesn't matter whether a/c is on or not. Is there a sensor that could be failing giving the controller a false signal? There are not fault codes.

 

Does anyone have the fan control circuit schematic? What drives the fan to come on? I see a water temperature gauge in the parts manual but no switch. The dash temp gauge is steady and fan will come on at 60 C.