I had this same problem with my 1996 Sunfire awhile ago. I took it to two mechanics and they both determined that it was a leaking head gasket and it was causing air to get trapped in the thermostat to make it run hot. Hope this helps you out. Good luck.
its somewhere right in the middle of the temop gage possibly a little higher then that.
Its overheating.... or the wire shorted
The average running temperature is 195-215 degrees F.
the sensor
Without a temperature guage, the most acurrate way would be to use a infrared temp. gun and aim it at the thermostat housing/radiator/water pump.
when you turn the heat on it comes out of the motor compartment in to the car,, further cooling the engine. A good thing to know if your car is running hot: turn the inside heat on full blast to help cool it down some.
what is the running temp for a Mercedes clk220
Probably 200 degrees F give or take 5 degrees.
It is cost prohibitive.
The temp sensors are in the sides of the heads under the exhaust manifolds one is for the gage the other is for the computer.
change your thermostat....
because the fan cools the engine...