How to lubricate a fan cooler in a Mercedes Benz?

Estimated:
I have a Mercedes Benz ML 400, with a problem that already identifies.
It is a lack of lubrication in a fan that has inside the fuse box, which is in the vain motor. This causes a very sharp and annoying whistle when it is generally started in cold mornings. After a few minutes disappear. The noise is so strong that despite being in the vain motor, it bothers a lot inside the cabin.
I tell you that this fan is always walking a few minutes after stopping the engine and taking the contact key. I imagine it is to cool the computer microprocessor. So when it starts with noise, there is no way to shut it up, you just have to wait.
I know that the fan (Fan Cooler) is in the fuse box, since I feel it but I do not see it, and I do not know how to disassemble it to lubricate it.
Can anyone help me?
Thanks and a hug for all,
Horacio