Cooling fan problem

Hi 

I have a Seat Altea 2005 2.0 TDI, I have a problem with cooling fun. When I turn of my car cooling fan start to work after 5-8 min and stay turned on stll spent the battery.

I think this problem hapend when I wash my car. My mechanic control for this problem but he cant find the problem. He check fus box, ECM, wires, and cooling fan all this parts are funcionating good. He substitute all this part with new part to find the problem but still the problem is my cooling fan stay on after I turn of my car.

I hope to help me someone

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