KHARBAT1

Drove my 2002 C320 twenty miles by the time I got there , steam started coming from under the hood , I opened the hood and watched all the cooling antifreeze run under the car . No broken hoses no leaks Just over boiling . I noticed that the Fan was not running when I start the car , shoud it ?
The Mechanic said the Fan was bad , he replaced it , NOW, the Fan runs as soon as I turn the key on , with a very high noise and before the car gets hot , is this the way the Fan should run or should it come on when the car is hot ? Thanks fo any explanation .

tjts1

The fan has a pwm controller that can vary it's speed as needed. If it's running all the time something is wrong. Find a better mechanic.

Bob T

If the fan is running on high at all times, I would first replace the coolant temperature sensor. If that does not fix the issue, you may have a bad ECU. I am assuming the fan runs on high with the AC off? If that is the case, if temp sensor does not fix the issue you most probably have bad ECU. I had same problem. I purchased a rebuilt ECU. I shipped my old ECU to these folks, they took off the files needed to transfer to the rebuilt ECU and I then plugged the new ECU in and all functioned fine including key fobs! Great company.