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I have a 2007 mercedes Sl550 67k miles. I have noticed the…

I have a 2007 mercedes...
I have a 2007 mercedes Sl550 67k miles. I have noticed the fan is running extremely loud and just seconds after turning car on when cold. It also seems to be whisteling a bit for lack of a better term.
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Answered in 2 hours by:
8/7/2018
Matt
Matt, Engineer
Category: Mercedes
Satisfied Customers: 23,486
Experience: Mechanical Engineer with 23 years experience in the auto industry, 8 yrs in formula 1 engine testing
Verified

Hello and welcome to Just Answer

I'm assuming you mean the engine cooling fan?

If so then I'd next use a scan tool to see what ECT ( engine coolant temp) is being recorded by the engine control unit

if its showing 200 deg F from engine start then I'd replace the coolant temperature sensor as the next step

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Customer reply replied 14 days ago
The temp gauge on dash is reading within norms but the fan is screaning ever when cold

The fan will also stay on if the freon is low to save the compressor from overheating with low fluid. So it may be worthwhile to have the freon level checked

Low side it usually between 25-45psi and high is 200 to 225

another possibility is the ECM has failed as the fan control module will default to having the fan on all the time if its not getting a signal from the ECM

I attach an image of the ECM in question

and effected part numbers :

a1121530879

a1121530079

a0245455832

a0245457032

a1121530779

a1121532679 and

a1121531279

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Customer reply replied 14 days ago
I will take the next step but I am traveling right now. Will be back tomorrow so I can be by the car if you have specific questions. My goal is to walk into repair shop with concrete ideas and not have them spin their wheels.

understood

please check the freon pressure next

Matt
Matt, Engineer
Category: Mercedes
Satisfied Customers: 23,486
Experience: Mechanical Engineer with 23 years experience in the auto industry, 8 yrs in formula 1 engine testing
Verified
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Hi
do you still need help?
Bear in mind that the site takes a deposit from you at the beginning and this is held by the site until you rate my answer at which point the cash is split between the site and the expert. I am only paid for my work on this question if you rate my answer, using the star system at the top of the screen. Please do not forget! If you're not pleased, also let me know because rating bad does not result in a refund, there are better options. Rating now will not close this post nor prevent further replies
Thanks Matt

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Matt
Matt, Engineer
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