I am also curious about the activation temp. I am guessing it is around 50F. I checked the manual and it just says it comes on depending on the temperature but doesn't say what temp. I don't think it controls anything or is controlled by anything, just the temp. I wonder what makes it turn off, or is it on all the time when it is cold? I am sure MB Doc knows!

Mike

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1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra