I just replaced the engine in an 02 C32 and have a problem with the cooling fan running slow speed at cold start up, and switching to fast speed 10 to 20 seconds after cold start. The fan never turns off, unless you shut the car off. Where is the sensor for the fan? The only sensor I changed was the temp sensor next to the thermostat.
I also changed the front brake pads, as the visit workshop reminder was on. good thing because there was only about 1/32" of pad left. The pads didnt come with new wear sensor, and the light is still on. The wear sensor is normally closed, and open only when worn down? I suppose i need a new sensor that has continuity.

 

its either the thermostat or the relay to the fan is going bad.

 

What does your water temperature on the LCD display say? I would think the fan would be triggered by the temp. The fact that it switches to high after 20 seconds or so tells me it is being commanded to do so and is not a relay.

If you watch your brake pad wear you can just cut the wires to the sensor and then twist them together.

 

So doing that in the rear-good tip!

 

It was the temp sending unit next to the thermostat. Either the SLK32 has a different one, or it was bad. If this part fails, the ECU must turn the fan on. The dash display showed no temp reading, and when I switched back to the C32 sender everything worked. Thanks For the replies, and I tied the wires together, and all is good.

 

yet another satisfied customer...