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Discussion Starter #1
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-c-class/1443583-auxialiary-fan-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.
 

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2013 VW Golf Sportwagen TDI, 2011 Mazda 2, 2000 E320 4Matic Wagon (retired),1994 C280 (retired)
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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.
 

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Discussion Starter #6
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.
 

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

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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.
 

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Also I just checked the relay (the blue one ) to find that the 15amp fuse inside it was blown. Getting a 15 amp replacement right now to see if the aux will come on.
 

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Mines working now too. The fuse fixed it. as soon as the thermostat hits 100 the aux fan kicks in. knowck it back down to 90.

Now i gotta get the clutch fan fixed so it dont go above 80
 

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Now i gotta get the clutch fan fixed so it dont go above 80
Exactly!! I can't believe what a difference a new fan clutch makes!! I am sorry that I didn't do it a year or so ago... you'll be amazed at the temp difference.
 

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Discussion Starter #14
When connected directly to the battery both my aux fans starts to spin, I never suspected the fault to be both auxfan motors, but good to rule out :)

I have read a lot about similiar problems but to me it seems like everybody with this problems has the two relays with the fuses on, one controlling the low speed and the ohter the high speed setting.
In my car though, there is a metallic or silver looking relay that according to this site: Your Parts Search Returned 5 Part(s) (look at the 3:rd relay from top) controlls the aux fan in some models. I also have a fan control module under the plastic cover in the driverside wheel arch.
Is this configuration unusual to the C200 W202 and how exactly is the fans controlled in this configuration? Does the relay have any role in this?
I am going to try to disconnect the coolant temp sensor tomorrow and then give an update in the forum.
 

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Discussion Starter #15
I have now attempted to get the fans going by disconnecting the temp sensor from the termostathouse, but the fans did not come to life.

I have attatched some images, one is of the control module inside the driver-side wheel arch the other is the relay I think could control the fans and the third is the aux fans themselves.
 

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I have now attempted to get the fans going by disconnecting the temp sensor from the termostathouse, but the fans did not come to life.

I have attatched some images, one is of the control module inside the driver-side wheel arch the other is the relay I think could control the fans and the third is the aux fans themselves.
did u try disconnecting the temperature sensor to see if the fans come on??
 

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Mines working now too. The fuse fixed it. as soon as the thermostat hits 100 the aux fan kicks in. knowck it back down to 90.

Now i gotta get the clutch fan fixed so it dont go above 80
First of all funny as sh*t, your thread title is...
Second, "Mines"? I thought you had to be four years old to use that word.

My laugh of the day so far...for the record is that correct or should it only be mine is? Got to know.

Almost forgot, what did you do before the fans went out, and from the looks of your pictures you should get some electrical cleaning spray and clean all of your connections and check as many as you can. And since your bay looks so dusty and dirty I would check ohter things that could be affected by the debris. Might not be the tool, but the wires to the tool too!
 

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First of all funny as sh*t, your thread title is...
Second, "Mines"? I thought you had to be four years old to use that word.

My laugh of the day so far...for the record is that correct or should it only be mine is? Got to know.
normally i wouldnt take someone on but this forum is the shit cuz its been savin my ass countless times.

1. Dude, the thread titile wasnt created by me.
2. "Mines" was a word i used cuz i was happy as hell that i finally got that shit workin. :D

im not even gonna bother lookin it up to see if it's grammatically correct. lol:thumbsup:
 

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Discussion Starter #19
did u try disconnecting the temperature sensor to see if the fans come on??
I did try to disconnect the temp sensor but the fans did not come on. I have now checked all the relays I had in the relaybox.
The relays had the following part numbers and I checked them on this mercpart-site to understand what they controll.

1. A 2028204626 CONTROL UNIT BLINKER/HAZARD-WARNG.-L.SENDER UNITS, HEATED REAR PANE,WIPER,TRAILER COUPL. (PARTSCATALOG.RU nr. 119)

2. A 0015426519 RELAY RETURN FLOW PUMP (PARTSCATALOG.RU nr. 119)

3. A 0015429919 RELAY TWO-TONE HORN (PARTSCATALOG.RU nr. 119)

4. A 2025420232 CONTROL DEVICE Replaces №: A 2025420532 (PARTSCATALOG.RU nr. 114)

5. A 0015420219 HEADLAMP WIPER / WASHER, BURGLARY ALARM SYSTEM , IMMOBILIZER (PARTSCATALOG.RU nr. 119)

So it seems a bit like there are'nt any relays controlling the aux fans, there is also the series resistor (have'nt really found on my car yet, have'nt been looking to hard either) that according to the site has something to do with the aux fans (A 0001583945 SERIES RESISTOR AUXILIARY FAN; PARTSCATALOG.RU nr. 262)

The device found in the wheelarch is according to the site: A 0165459632 CONTROL UNIT ADDITIONAL FAN (PARTSCATALOG.RU nr. 264)

I have not bought any electric cleaning spray yet, will have to do that and also really check all the cables.
 

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I did try to disconnect the temp sensor but the fans did not come on. I have now checked all the relays I had in the relaybox.
The relays had the following part numbers and I checked them on this mercpart-site to understand what they controll.

1. A 2028204626 CONTROL UNIT BLINKER/HAZARD-WARNG.-L.SENDER UNITS, HEATED REAR PANE,WIPER,TRAILER COUPL. (PARTSCATALOG.RU nr. 119)

2. A 0015426519 RELAY RETURN FLOW PUMP (PARTSCATALOG.RU nr. 119)

3. A 0015429919 RELAY TWO-TONE HORN (PARTSCATALOG.RU nr. 119)

4. A 2025420232 CONTROL DEVICE Replaces №: A 2025420532 (PARTSCATALOG.RU nr. 114)

5. A 0015420219 HEADLAMP WIPER / WASHER, BURGLARY ALARM SYSTEM , IMMOBILIZER (PARTSCATALOG.RU nr. 119)

So it seems a bit like there are'nt any relays controlling the aux fans, there is also the series resistor (have'nt really found on my car yet, have'nt been looking to hard either) that according to the site has something to do with the aux fans (A 0001583945 SERIES RESISTOR AUXILIARY FAN; PARTSCATALOG.RU nr. 262)

The device found in the wheelarch is according to the site: A 0165459632 CONTROL UNIT ADDITIONAL FAN (PARTSCATALOG.RU nr. 264)

I have not bought any electric cleaning spray yet, will have to do that and also really check all the cables.
http://www.benzworld.org/forums/w202-c-class/1443583-auxialiary-fan-question.html

check the diagram on page 1. see whats goin one with yours i have a c220 and mine matches exactly with the diagram the 1st poster put up there.

So u know, when I disconnected the sensor (the one on the driver side under the plastic benz logo right above the water pully, my fans came on. but later i came to find out anyway that my relay 1 fuse was blown anyway. i dont know if it was the level 2 fan that came on, but i CAN tell u both them things was turning, and it was loud as hell, even though my relay fuse 1 ws blown. i dont know what wouldve happened if relay 2 fuse was blown as well. the fuse sits right inside of the relay as described in the link. it was a 15amp. i replaced it with 25. problem solved.
 
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