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Stan, Mercedes Technician
Category: Mercedes
Satisfied Customers: 3526
Experience:  Technical support engineer
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I have a 2012 C Class and the engine used to run at around

Customer Question

I have a 2012 C Class and the engine used to run at around 80 degrees F as the normal temperature - Now each time I drive the car the engine always goes above 80 degrees F (up to the max of 120 degrees F) and the engine fan comes on very loud. Once the engine reaches 120 degress F then I start to loose power in the engine.
Is the fan controlled by a switch or by the ECU? - Why is the engine temp getting so high? Does it sound like the fan is not working properly?
Submitted: 2 years ago.
Category: Mercedes
Expert:  Shantal-Mod replied 2 years ago.
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Customer: replied 2 years ago.


I am still waiting for an answer for this question...

Expert:  Stan replied 2 years ago.
The fan module has a built in controller, which recieves commands from ECU and climate control unit. Depending on the request, fan speed is graudally raised or lowered.
Normal working temperature is about 80-90 degrees Celcius ( 180-190 Fhrenheit).

120 degrees Celcius is way too much.

The best way to test the fan module is to do fan actuations with Star Diagnosis computer.
It is possible to increase the fan speed in steps of 10%. If this cannot be carried out-fan module is faulty.
Faulty fan module can go from 0 to 100% speed. But if the lower speeds cannot be acheived, engine will overheat.

Best Regards,