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Matt, Mechanical Engineer
Category: Mercedes
Satisfied Customers: 22765
Experience:  BEng hons Mech engineering, in auto industry 22 years
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My Mercedes c220cdi Se blueffincy se w204 2009 uk the fan

Customer Question

My Mercedes c220cdi Se blueffincy se w204 2009 uk the fan turns v high speed on radiator fan after one min of car starting up even the engine is cold change the thermostat with sensor get aircon checked that's fine change the air flow meter change the whole fan advise by Mercedes garge still the problem is same now really really fed up
Submitted: 1 year ago.
Category: Mercedes
Customer: replied 1 year ago.
Ecu according to Mercedes it's fine but they said it's not communicating with radiator fan
Expert:  Matt replied 1 year ago.


for the fan to run all the time then either its a fault with the coolant temperature sensor , the wiring from the coolant sensor or the fan control unit itself

so I'd begin by checking the coolant sensor wiring for damage/ hard sections and corroded connections

if thats all OK then I'd consider replacing the fan control unit

Customer: replied 1 year ago.
Where is fan control unit located in this car and wot it looks like ? Thanks
Expert:  Matt replied 1 year ago.


the fan controller image was attached in my last message and is usually attached to the back of the fan itself, see the attached image - its the little black box about the size of a family pack of matches

Expert:  Matt replied 1 year ago.

2nd pic