My 2010 Mercedes R Class has a fan in upper right corner of engine compartment that runs for up to 2 hours even when the engine is off
The dealership has tried to find the problem twice to no avail.....

 

You in the US? Contact MBUSA or zone rep. Or go to another dealer.

I have no idea if MB has zone reps elsewhere or how resolving dealer issues works in other areas.

 

Believe it or not, I had to contact MBUSA to even get the dealership to continue to evaluate the car. They thought since no codes appeared everything was fine!!! After 3-4 phone calls and never a return call from MBUSA, I called and said I was not getting off the phone until I got an answer. One 'technician" tried to tell me that I had to "go with" whatever the dealership said, which was that it was normal for a fan to run for hours after the vehicle was turned off. Unbelievable!! This is my fourth or fifth Mercedes, but it might be my last! So much for outstanding and exemplary service.