I have a clk230 Kompressor Coupe and would like to
1) test if the outside temperature display is working
correctly.
2) know where the sensor for this display is located

Don't know where it is for CLK. On my W202 it's at the bottom of windshield at passenger side, just below plasic grill. Of course, outside.

Put a thermometer at that position then compare the reading, you should have answer.

Charles

The sensor is at the bottom right hand side of the lower grill next to the foglamp. You will notice a small black probe sticking out.

Remember, the probe measures "ambient" temperature, not "actual". Otherwise, you would get all sorts of variable readings depending on your speed (i.e. wind velocity affecting the readings).

The temperature readings at initial startup will not be correct. It stabilizes after about 5 minutes of driving.

So, I'm not sure if a simple thermometer test will do the trick...