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Marty, Mercedes Technician
Category: Mercedes
Satisfied Customers: 53293
Experience:  Bosch Certified Master Tech. Over 35 years experience.
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2005 ml350: radiator / wont shut..disconnect..reconnect

Resolved Question:

I own a 2005 ML 350 and the radiator/cooling? fan won't shut off after I shut the car off, I have to disconnect the battery, and then sometimes when I reconnect the battery, the fan starts up again. this time it's been running for an hour, I am worried the battery will go dead.
Submitted: 4 years ago.
Category: Mercedes
Expert:  Marty replied 4 years ago.

eurotec :

Hi, it sounds like you have a bad cooling fan control module. If the module shorts out the fan will run continuously.

eurotec :

Actually on your car there may not be a module. Do you have the two fans in front of the radiator?

Customer: I do
eurotec :

Ok, try removing fuse #44 in the fuse box and see if the fans turn off.

eurotec :

Full Size Image

Customer: Would that fuse be in the box by the engine or the box by the passenger door ?
eurotec :

under the hood

Customer: That worked it off now !
Customer: Do I just replace that fuse ?
Customer: Do I replace fuse ?
eurotec :

sorry I was pulled away

eurotec :

Did the fan turn off when you removed the fuse?

Customer: It did
eurotec :

Ok, then you may have a bad fan relay. Let's try removing the relay and swapping it with a similar relay in the fuse box. I will post a picture.

Customer: Ok
eurotec :

I need to change computers. Don't go away.

Customer: Ok
eurotec :

Full Size Image

eurotec :

Remove that relay and replace with another one of the same kind in the fuse box.

Customer: Where would a replacement one be in the box ?
eurotec :

You will just need to remove one that looks just like it.

eurotec :

This is only for a test

Customer: I removed a different one in the fuse box and put it in that spot
eurotec :

Ok, did the fan remain off?

Customer: Yes it did
eurotec :

Ok, then the relay is bad.

eurotec :

Go ahead and get a replacement and you should be fine.

Customer: So then I need to replace that grey relay box I took out ?
Customer: Ok thanks so much :-)
eurotec :


eurotec :

You're quite welcome

eurotec :

Please don't forget to click Accept so I can get credit for my help today.

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