Electrical cooler fans, overheating - Benzworld.org - Mercedes-Benz Discussion Forum

olli_m89 · 07-03-2009, 08:40 AM

Hi!
I have a 96' C200, the car has one viscous fan in front of the engine and two electrical fans between the grille and the radiator.
The problem is that the electric fans does'nt start running at 100 C as i understand they should.
I called the MB dealer and explained my problem, they said the electrical fans are controlled by some kind of controlmodule I don't know if they ment the ECU.
I found a thread (http://www.benzworld.org/forums/w202...-question.html) where some people had problems with the fans because of a relay, but I couldn't find the mentioned realy in my car.

(I've attached an image of my relaybox.)

Does anybody have tips on what to do?

I have also noticed that the coupling on the viscous fan is worn and should be replaced, while that could explain some of the overheating problem it does not explain why the electrical fans doesn't work.

I am going to flush the coolingsystem today and clean the radiator core to see if it gets any better.

bmeister · 07-03-2009, 09:10 AM

Is this what they were referring to? Do you have one? Second pic was labeled resistor. . B

olli_m89 · 07-03-2009, 11:45 AM

Yes I have one of those, it is under the left-side wheel arch, is that the control unit?

jlomon · 07-03-2009, 01:05 PM

Check the fusebox to see if there are any fuses labeled for the auxiliary cooling fans. Perhaps your model has moved the fuses there instead of in the relay box like on my older W202. Will your auxiliary electric fans come on if you turn on the air conditioning? They should come on automatically when you do this.

I agree with you that your viscous fan is probably the reason you are overheating if you have verified that it is not operating. The viscous fan is supposed to provide the cooling power under normal circumstances. The auxiliary electric fans come into use with the air conditioner or when some other part of the cooling system has failed, causing the temp to move over 100C. As you said, you have two separate issues here.

ghartin · 07-03-2009, 04:01 PM

Nice picture. Is one of those relays the famed fuse #32?
Gene

olli_m89 · 07-03-2009, 04:23 PM

Quote:

Originally Posted by jlomon

Check the fusebox to see if there are any fuses labeled for the auxiliary cooling fans. Perhaps your model has moved the fuses there instead of in the relay box like on my older W202. Will your auxiliary electric fans come on if you turn on the air conditioning? They should come on automatically when you do this.

I agree with you that your viscous fan is probably the reason you are overheating if you have verified that it is not operating. The viscous fan is supposed to provide the cooling power under normal circumstances. The auxiliary electric fans come into use with the air conditioner or when some other part of the cooling system has failed, causing the temp to move over 100C. As you said, you have two separate issues here.

I have gone through all of the fuses, but there were no burnt fuses. The viscous fan is operating but I suspect the coupling is worn because when the engine is hot it should be stiff and stop almost at the same time as the engine does when the engine is turned off, but in my case it keeps spinning for a while.
Now I have changed the coolant and flushed the system, I think this actually helped, now the temperature is very stable, allthough the outside temperature has dropped like 10 C compared with yesterday so that has probably helped a bit.
The aux fans does not come on when the AC is turned on.

Chris A · 07-03-2009, 06:17 PM

Can you check to see if there is any voltage to the fans.

olli_m89 · 07-04-2009, 02:09 PM

I will have to do that, does anybody know how exactly the aux fans are controlled?

VicC220 · 07-13-2009, 08:43 AM

I thought that the Temp Sensor tells the relay when the Aux fan should come on. I was told when the car is running at a decent temperature, andthe air sensor is disconnected, the aux fan should come on.

when the sensor is disconnected:
If the aux fan does not come on that means the aux fan has an issue.

If the aux fan does come on, that means the sensor or the relay is bad one of them is not telling the aux fan to come on.

in other words the sensor should be relaying the aux fan when not to come on.

This is what i heard from a mechanic. Im gonna try it right now. the sensor is under the plastic piece with the Logo on it right in the front of the engine above the water pump. theres 2 of them on the drivers side.

VicC220 · 07-13-2009, 08:47 AM

I just disconnected the temp sensor on the right hand side and the fans came on after 2 seconds. thems shits were roaring