The auxiliary fans in the M119 engine come on at 107C and 115C (I believe). There is also a pressure switch that activates the fans based on A/C refrigerant pressure.

So - in hot weather your car running around 100C with the A/C on is not abnormal.

I, however, think this is too hot. So do many others. Jim F., a regular poster on this website, has his own site that shows instructions for setting the fans to come on at a cooler temperature. It costs about $1.00 for a resistor, if you buy it at radio shack, or you can buy his ready made harness that plugs into the coolant temp. sensor for $30.

I did the mod with radio shack resistors, and now my car never gets above 95C. It makes me feel a whole lot better. There's too many expensive parts to cook in the M119 at 105C.

Here's the link to Jim's website (great for much more than cooling problems too).

http://pages.prodigy.net/jforgione/MB_CTS.html

Troy
1995 E420 82k