Originally Posted by tjts1

I changed mine from 105c to 90c with a 700ohm resistor in parallel but you can choose any temperature with different value resistor. 95c trigger point would require a ~766 ohm resistor. 750 ohm is an easy off the shelf solution. I also changed my thermostat from the stock 87c to 79c. Even without a clutch fan, the electric fans rarely trigger. I also added a backup switch in the dash if the temp sensor ever fails.

105c on a daily basis with a dead clutch fan is death to the headgasket.

I don't think mercedes takes it as a personal offense every time somebody modifies their 20 year old car. The fact of the matter is even if you keep your cooling fans in tip top condition, after 100k+ miles the radiator gets loaded up with all sorts of road debris between the fins. The radiator needs to be removed and thoroughly cleaned both inside and out to bring it back to its original cooling capacity. In my case I also had to straighten out a few hundred fins damaged by the brilliant 'mercedes specialist' who worked on it previously.

Its an NTC (negative temperature coefficient) temperature sensor, not a switch. Early cars (pre 87) have a temperature switch and adding a resistor to these won't work.
Keep in mind that using an 1100 ohm resistor as in the article ( http://pages.prodigy.net/jforgione/MB_CTS.html ) wont give the same results in our cars. The W140 uses the same temperature sensor but the fans trigger at 100c or 310 ohm. The M103/104 trigger at 105c or ~270ohm. You have to recalculate the resistor values for your specific target temperature.
http://www.sengpielaudio.com/calculator-paralresist.htm
The known data points for this sensor:
115c = 200 ohm
107c = 250 ohm
100c = 310 ohm
80c = 560 ohm