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C-Class (W202) 1995-2000: C 200 CDI, C 220 CDI, C 270 CDI, C 180, C 200 K,C 230 K, C 220, C230, C 280

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Old 11-14-2007, 07:36 PM   #1
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Unhappy Radiator fan always on HIGH, regardless of weather or a/c, this is not normal.

I want to first start off stating that this problem is not normal. I turn the car ON, and the radiator fan turns on about 5 seconds after the car is started, and stays on the entire time the car is on, it sounds like what it WOULD sound like IF it was a very hot day with the a/c on. But this occurs regardless of the situation, it always turns on, and at full speed.

This has been going on for about 2 months now and I am finally getting around to posting about the problem. If you could imagine, I can't just leave this problem sit before more problems start occurring, so I've gotta figure out the problem soon.

If anyone has any tips at all or knows what the problem is, please let me know on this thread, thanks.

I will make sure that this thread lives until I solve this ridiculously annoying problem.

My car is a 98 W202. Thanks much for reading!

PS, a couple months before this I was having the "EC light on" problem (reset it), if that has any significance at all. Just throwing it out there.
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Old 08-11-2010, 01:40 PM   #2
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Engine fan turning on and off . . .

Bumping this.

I have a 94 C220 and the fan comes on and off while my car is on, regardless of temperature, and immediately after starting. My CEL is on a well. . .

Any help would be appreciated.
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Old 08-12-2010, 11:25 AM   #3
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Quote:
Originally Posted by stevodotorg View Post
I want to first start off stating that this problem is not normal. I turn the car ON, and the radiator fan turns on about 5 seconds after the car is started, and stays on the entire time the car is on, it sounds like what it WOULD sound like IF it was a very hot day with the a/c on. But this occurs regardless of the situation, it always turns on, and at full speed.

This has been going on for about 2 months now and I am finally getting around to posting about the problem. If you could imagine, I can't just leave this problem sit before more problems start occurring, so I've gotta figure out the problem soon.

If anyone has any tips at all or knows what the problem is, please let me know on this thread, thanks.

I will make sure that this thread lives until I solve this ridiculously annoying problem.

My car is a 98 W202. Thanks much for reading!

PS, a couple months before this I was having the "EC light on" problem (reset it), if that has any significance at all. Just throwing it out there.
There are a bunch of causes to having a fan turn on high regardless of temp. Some more information regarding your vehicles cooling system would help. Do you have a viscous engine fan and aux. electric fans or just the electric cooling/engine fan? Even a pic of your engine bay would help.

I had a similar problem, my problem started with a dealership change of my climate control head unit. My car is a 2000 C280 with an electric cooling/engine fan only. When I would start my car the fan would come on and stay on high until the car was shut down regardless of temp. The dealership told me this was normal so I believed them for 3 years! Finally I researched and found out that the climate control head unit needs to be version coded correctly in order to operate the cooling system in your vehicle properly. There is a document that explains how to do this which I can forward you if you feel it is your situation.
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Old 07-09-2011, 01:37 PM   #4
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Red face

I have this same problem for nearly 6 years now, I have a W202 1999 C200 automatic. First happened after the car was stood still for a long while after battery died. Then the electronic ignition switch had failed, replaced it for another one coded by MB in Germany to my keys.

Then after the coolant/washer low fluid light would come on automatically from turning the car on. With the engine fan running at high speed. At times it may cut off, but then it would come back on after about 2 mins and stay on permanently for around 20 mins or more.
I went through countless parts to try and fix the problem - with no success. Parts bought virtually all brand new from MB.
Coolant low level sensor
Windscreen washer fluid sensor
Engine thermostat
Engine coolant temperature sensor
AC engine compressor (this ended up failing about 2 years ago)
Engine cooling fan
Engine Cooling fan module (mounted under front nearside wheelarch inner panel)

Just been reading another thread and they said a float is inside the coolant expansion tank, so may just go and check that out to see if its dislodged.
I even used Star DAS connected to my laptop, but it does not give anything specific to the problem. I then even cleared all faults, but still same thing.

I had import the car abroad 10 years ago, I have had nothing but problems, mainly electrical, if I had known they would be like this I would NEVER have bought this car, and went for aother model or manufacturer.

To make matters worse there is no MB dealer on the island. I have worked on many vehicles and clued up about cars, but this one is weird.
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Old 07-09-2011, 04:28 PM   #5
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not difficult to fix.. Do you have star diagnose?
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Old 07-10-2011, 02:30 AM   #6
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Yes i do have star diagnosis, but it did not pinpoint an exact problem, which I was very suprised and disapointed.
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Old 07-11-2011, 06:18 PM   #7
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first of all connect star and do a short test for me and post the results here pls.
Also print out and post here all the variant coding pages from ICM (KI), AAC, EIS

Last edited by Russell Ormerod; 07-11-2011 at 06:23 PM.
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Old 07-13-2011, 10:56 AM   #8
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Question

I had conduct two tests on Star. The second one produced more faults, I guess this was because I had turn the engine on and then also had turn the ac on.

First Test
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2nd Test

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I also went through almost all the wiring on the car with no success. From the radiator fan, back to the ECU and the fusebox. Also loosened the earth wire that comes from the fan control unit which the earth wire is mounted on the inner wing under the washer bottle. Even sprayed and cleaned them with electrical contact cleaner.
One thing I have realised that the fan controll unit is permanently supplied with 12v even if the ignition is off. Even fuse 38 (big orange 40amp) and fuse 41 (standard blue 15amp) has voltage going to it even when the engine is off.

Also been looking at the new fan control unit supplied by MB and notice it has a different part number A 025 545 33 32, which I guess superceeded the old one A 018 545 99 32. Even if I plug the old fan control unit back in there seems to be no difference with the fault.

Last edited by c200 Goblin; 07-13-2011 at 11:05 AM.
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Old 07-13-2011, 11:09 AM   #9
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I am not sure what it means by transfer coding to new module. I never did this though.

ME2-SFI Menu

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Old 07-14-2011, 02:01 PM   #10
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why cant you communicate with KI intrument cluster?
check the coding in instrument cluster and ezs pls
must be coded for engine suction fan

Last edited by Russell Ormerod; 07-14-2011 at 02:04 PM.
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Old 07-14-2011, 02:32 PM   #11
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Ok I would try that out, did not realise it was in the instrument cluster menu.
So would I have to transfer coding or something to it.

Quote:
Originally Posted by Russell Ormerod View Post
why cant you communicate with KI intrument cluster?
check the coding in instrument cluster and ezs pls
must be coded for engine suction fan
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Old 07-15-2011, 10:29 AM   #12
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I just want to make sure your car is setup correctly first before we go to in depth testing. Your EZS,KI,ME,AAC are all involved in running your fan, Although ME is what sends the signal. That why i want to see the Coding For Cluster(KI) AAC and EZS. your fan controller has two thick wires a ground and a battery supply. also 2 thin wires. one is ignition and the other is the PWM signal from ME. One other test you can do! If you go into actuations in your ME unit are you able to slow your fan speed down, or does it still run at MAX?
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Old 07-16-2011, 01:17 PM   #13
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I think I have virtually given up with this car, I think I have tried everything. One thing I have noticed now is that the washer fluid low level sensor does not have any voltage going to it with the ignition on. Even by disconnecting the sensor. I have even remove the dashboard instrument cluster and splice the feed lead to the washer sensor and still had no voltage.
I tested the coolant low washer fluid sensor which has around 4.5 volts going to it. I had even bridge this to the washer fluid low pump but it still did not stop the fan racing at full speed.
I have even now changed the SAM module under the fusebox wing with no success. The only way I can get the fan to stop running at full speed and the low coolant light to go out, is if I remove fuse 41 which is 15 amp. The coolant fan circuit has two fuses, one being 38 (40amp) and 41 (15amp). The fan would operate normally - only downside is, that all the functions from the wiper stalk would not work (i.e. indicators, wipers, washers)

I have put the coding below of the various units. EIS (which is EZS), ME, AAC (which is TAU), and KI.
There is very little you can do in these menu's appart from control various sensors and see values,, but nothing I can see at setting the fan etc.

I was able to control the fan speed in ME acutations, where the fan speed is automatically at 55%, then you can vary it and slow it down. If fuse 41 is pulled out and the fan is not racing out, when you log into this menu it is automatically at 100%.

I now really have a feeling it may either be the instrument cluster or the ECU at fault.

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Old 07-16-2011, 07:51 PM   #14
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Also I have just realised if I remove fuse 19, which is a 10amp fuse and controls the brake lights and instrument cluster; it also stops the fan from racing out heavily and turns the low coolant light off.
I am really beginning to think there may be a fault with the instrument cluster internally.
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Old 07-19-2011, 07:16 AM   #15
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Look in "VARIANT CODING" not control unit version!
KI AAC EZS check all and show me the results.

put all fuses back...

If you can control the fan from ME. thats a good sign. It means our fault is further back. Once I am happy with the CODING we can check the problem with the level light!
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Old 07-20-2011, 12:09 PM   #16
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I have cracked it, FINALLY at long last. Thanks for your help.
whilst going through the list looking for variant coding, only one of the three had a menu that said variant coding, being the TAC Automatic Temperature control.
The others seem to access this through control module adaptations.

Ill post the rest of it here later, just got to go out. But the problem was the Ignition Switch Module EZS was not set properly, I guess from when I changed the failed ignition switch module a few years ago. It had the vehicle model as unknown and the setup as right hand drive unknown.
So I had set it to W202 and right hand drive. Other options were the estate S202 and left hand drive.

Since that its working ok.
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Old 07-22-2011, 04:31 AM   #17
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well done, for finding it, i assumed it was a coding issue
enjoy
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Old 08-01-2011, 07:30 PM   #18
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radiator cooling fans both on 1995 c200

Hello,
Following up with another cooling fan problem. Bought a 1995 c200 in malaysia, auto with 170k on it, and both of the forward small fans that cool the radiator are always on from the instant I turn on my key till i turn it off. Took it to a garage and the Chinese guy with medium English skills hooked up a laptop and it said something like "Could not connect to ECU" and he gave up. When he removed that electrical connection from the thermo probe that connects to the forward part of the engine, both fans acclerated up to a higher speed. I removed the specified fuse from the box that is also for the wipers and it shuts the fans off but of course don't want to do that for driving. Is Mr Ormerod still out there? You seem very good at this stuff....
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Old 08-02-2011, 04:51 AM   #19
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I am here
Well it sounds like your fan is running on first speed
which is usually a AC pressure problem
Does your AC work and cool properly?

The AC pressure sensor is fitted to the the Reciever dryer bottle.

There are a few version to this system so the tests u need to do may vary depending on what is fitted to your car

the sensor that you unplugged on the cyl head is it a Blue 2 pin sensor?
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Old 03-25-2012, 05:17 PM   #20
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Smile If Russel is still there :-)

Hi Russel,

Have just brought a Mercedes C240 W202 right hand drive. Car has only done 56k miles and has Mercedes FSH and is in excellent condition. Engine is very clean and all levels are topped up.

Yesterday the engine fan came on at full power after I returned from a drive and did not stop even when the keys were removed.

Think it would have run like this until the battery ran out of power. Only way to stop the fan is to remove fuse for the fan.

When the fuse is re-connected (even with no keys in the ignition) fan comes on immediately at full power even when the engine is cold.

Is there a way to fix this problem easily?

Many thanks for your help.

Vadim
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Old 04-07-2012, 11:29 AM   #21
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PLEASE I LIKE SOMEONE TO HELP URGENTLY WITH THE PART NUMBER OF ENGINE COOLING FAN MODULE,MOUNTED UNDER FRONT NEARSIDE WHEELARCH INNER PANEL OF MERCEDES C200 1999 MODEL URGENTLY. THANKS
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Old 04-12-2012, 03:39 PM   #22
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Originally Posted by Vadimovich View Post
Hi Russel,

Have just brought a Mercedes C240 W202 right hand drive. Car has only done 56k miles and has Mercedes FSH and is in excellent condition. Engine is very clean and all levels are topped up.

Yesterday the engine fan came on at full power after I returned from a drive and did not stop even when the keys were removed.

Think it would have run like this until the battery ran out of power. Only way to stop the fan is to remove fuse for the fan.

When the fuse is re-connected (even with no keys in the ignition) fan comes on immediately at full power even when the engine is cold.

Is there a way to fix this problem easily?

Many thanks for your help.

Vadim
Sounds like the suction fan control module to me, especially if it runs with ignition off
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Old 04-12-2012, 03:40 PM   #23
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Quote:
Originally Posted by GODWIN ONWUOKWU View Post
PLEASE I LIKE SOMEONE TO HELP URGENTLY WITH THE PART NUMBER OF ENGINE COOLING FAN MODULE,MOUNTED UNDER FRONT NEARSIDE WHEELARCH INNER PANEL OF MERCEDES C200 1999 MODEL URGENTLY. THANKS
You can try 018 545 99 32 or ph MB for superseeded part number
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Old 05-12-2012, 11:05 PM   #24
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I just had the same problem and when I read the W202 Service manual for 94-00 c class and on page 83.00-4 under climate control it shows you how to set the version coding to have the fan run normal by using the Climate Control Panel. It also has all the corresponding Coding numbers Very easy to follow.
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Old 06-03-2012, 06:32 AM   #25
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Hi all,

I wonder if somebody can help, my problem seems similar(ish) to the thread subject.

Mine is a 1998 C180 auto with a/c and 130,000 km. Recently purchased.

First long trip - after 250 km at 100-140 km/h the yellow radiator warning light came on and off a couple of times over the space of 20 mins (water level in rad was fine). When I reached my destination the radiator fan came on after I had turned the ignition off and remained on to flatten the battery. Recharged the battery took it for a quick spin. Same thing happened.

Had to remove fuse 38 (RAD) to stop the thing killing the battery.

Any advice lads & lassies?
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Old 06-03-2012, 06:32 AM
 
 
 
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ac, benz, c320, climate, control, cooling, electric, engine, fan, head, high, mercedes, radiator, stays, stuck, turning, working



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