Hello, I have found that my interior fan only runs on level one and probably level four level two and three. In between the same speed as four therefore my guess of the fan resistance is broken. Unfortunately, I found on YouTube and on the Internet no instructions how to exchange this or where to find it. Has any of you done this before and can roughly explain to me how to swap the part and first where to find it? he plans or instructions I would be very grateful to you My SL 500 is from 08 1991