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Radiator fan always on HIGH, regardless of weather or a/c, this is not normal.

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Radiator fan always on HIGH, regardless of weather or a/c, this is not normal.

 
Old 06-21-2012, 09:13 AM
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C200
Not sure if its the same problem I had, but you may have to get it hooked up on DAS so you can check to see if the car model is set correct in the Ignition Switch control unit. Needs to be set as a W202 saloon and right hand drive.

Originally Posted by W202.BAC View Post
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 06-21-2012, 09:53 AM
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As posted before the problem is due to when changing the electronic ignition switch. The coding in the menu needs to be changed with DAS on the computer. If this is not done the fan module does not seem to know what the car is hence why it turns on full speed as a precaution.

To access this, you in DAS, after running a test. Go to EZS Electronic Ignition Switch - ELCODE.


In EZS functions menu, go to option 5 being Control module adaptations.


next in the CM adaptations in the EZS select option 2 being read/change coding


In Read/Change coding in the EZS now it may show vehicle model as unkown, model as LHS.

This needs to be changed by entering them and changing 01 to W202 if you have the saloon and S202 if you have an estate.

The second would be to change in 02, option 2 being Right hand steering.
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Old 07-30-2012, 01:41 PM
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I am having the same exact fan issues after purchasing a car that sat for a while and lost battery power. When I replaced the battery and run the car the radiator fan will run constantly. I have verified that the ac system is pressurized because I have read that controls the fan turning on and off as well. Is the STAR DAS system the only way to verify and switch the coding?
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Old 08-14-2012, 05:24 PM
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C220 CDI SPORTS COUPE 2001
Yepp Star is the only wayy as Mercs these models have 1 circuit which has 100 sensors, n wires etc so star will pin point where you can start and work around that area.. you can still check basics like sensors curents with an volt meter like amps ohms etc..
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Old 12-05-2013, 10:50 PM
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Sometimes when the cooling fan is on high speed the problem could be the ecm. Since the ecm controls the fan. Another thing to check is the mass air flow sensor. Here is a video showing the fan on high.
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Old 02-18-2014, 10:21 PM
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2010 c63
guys, please help. I have a 2010 c63 with a similar fan issue. after about 10 secs of a cold start the fan turns at high speeds and does not stop. I also noticed that when this happened, my AC also stopped functioning. Can anyone help please. Thanks
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Old 02-19-2014, 09:32 AM
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s500 2003
Mercedes Benz cooling fan problem

If you watch the video then you should be able to determine if the symptoms are the same. I can't tell you whether or not your mercedes ecm is bad without inspecting it. But I can tell you that a fan running constantly on high speed is a sure sign of a bad ecm. We see this a lot for C240 and C320 models. If you want us to test it we have test vehicles that we can plug your ecm into and see if the symptoms persists. This is the best way to tell if the unit is bad. A visual inspection of the board is not good enough.
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Old 03-05-2014, 05:35 AM
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If you have a C63, it may still be under warranty, so take it back to a dealer. If not maybe take it to a trusty independent. I am sure it is a similar thing that happened to me. Trouble is Mercedes use canbus to control the fan and is coded to the electronic ignition switch annoyingly. So if you had any of those components changed or battery gone flat or disconnected for a while, guarantee, it would bring up these gremlins.

Originally Posted by dvyce View Post
guys, please help. I have a 2010 c63 with a similar fan issue. after about 10 secs of a cold start the fan turns at high speeds and does not stop. I also noticed that when this happened, my AC also stopped functioning. Can anyone help please. Thanks
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Old 05-16-2014, 08:38 PM
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1997 C230
Cooling fan not operating at all

I have a 1997 C230 with an inoperable cooling fan. The fan itself works when hot-wired and all the appropriate fuses are good. I swapped out the cooling fan controller underneath the wheel well with a used unit to no avail. Granted, it was used, but after reading your thread concerning fans that operate on high all or most of the time, I came to realize that fan issues can get exceedingly complex rather quickly.

Some background on the vehicle:The car had sat for years (with a dead battery) before I installed a used 90k engine. the car itself has 179k. That said, it runs quite well except for the inoperable cooling fan. Something that may or may not be of importance: after the "new" engine was installed, I had to take it to a Mercedes shop to have the "immobilizer" code reset in order to get the car to run for more than a few seconds. Apparently the computer was shutting down the fuel pump and/or injector pulse immediately after start-up. In addition, the AC doesn't function, because there is no refrigerant in the system, and I'm in no hurry to fix it, because I live 9000 feet up in the Rockies and have little use for it. Although it's probably serendipity, I, too, have a low coolant level light on, but with adequate coolant.

After reading your thread concerning cooling fan problems, I now wonder if the ECU, and not the fan controller unit, could be at fault. The check engine light is not on, nor have I pulled any codes other than an occasionally cranky O2 sensor. Wouldn't a bad ECU trip the light?

What are your thoughts? It appears there are other possibilities like programming errors or nonfunctioning AC in addition to the usual suspects such as the fan controller, fuses, and the fan motor. How do I narrow the field?
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Old 05-17-2014, 06:56 AM
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As you have said, you had the battery disconnected for a long time. This is what had happen to mine. I guess the ECU has some kind of internal backup memory in it. Maybe after a month or more, it would loose all info, so it does not know what car model it is, whether saloon or estate, or right/left hand drive.
So then it goes to a default parameter that would put the coolant light on even though coolant is in the car. If you had ac refridgerant in, it would possibly put your fan to run at high speed.


You need to get your car programmed in DAS to select what model it is. Don't think its a bad ECU.
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Old 05-17-2014, 09:14 AM
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1997 C230
Thanks c200 Goblin. Can I download DAS or STAR? Otherwise where do I find it? Tom
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Old 05-17-2014, 09:29 AM
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1997 C230
Basically I'm just trying to get the fan working on my old 1997 C230. If I am to do it myself, will that necessitate getting DAS or STAR or whatever with all the whistles and bells, or can I buy or download some sort of inexpensive alternative that might utilize my OBDII code reader, which has a computer port on it, as an intermediary? Or is the dealer's $200 potential fix the best option? My fear is that going to the MB dealer might be a bit like opening Pandora's box, releasing a litany of automotive ills to get things right(such as refurbishing the AC system) that I can ill afford. I'm just trying to end up with a decent driver, not a restoration project. After all, it's only a naturally aspirated C230, not a 600 Pullman.

Last edited by quaspero; 05-17-2014 at 11:02 AM. Reason: to clarify that what my goal is concerning my 1997 C230.
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Old 09-25-2014, 12:15 AM
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2003 C180 COMPRESSOR FUN RUNS ALL THE TIME

Hi there guys name wayne i have 2003 c180 compressor
and the moment i put my key in the ignition and turn the key,after say 5 seconds the fan starts to run at full speed
what i have done replaced complete fan and control unit but no luck there
can anyone pls help this is driving me nutts pls
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Old 09-30-2014, 11:12 PM
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Your best bet would be to take it to an indie, main dealer, or buy a DAS import from China/Hong Kong. That is the only way you would solve it. Don't waste money buying more parts. I did exactly this and it solved nothing.
Only way is to change the variant coding. This can go blank in the field if the key ignition has been changed or the car's battery has been disconnected for a few months.


Originally Posted by hutch69 View Post
Hi there guys name wayne i have 2003 c180 compressor
and the moment i put my key in the ignition and turn the key,after say 5 seconds the fan starts to run at full speed
what i have done replaced complete fan and control unit but no luck there
can anyone pls help this is driving me nutts pls
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Old 04-07-2017, 12:13 PM
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2002 Mercedes CLK 320
This is what happened to my 2002 CLK320

Originally Posted by Capt View Post
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.
Please, Please, Please can you send me the document?????

Thank you!!!! Glynis
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Old 04-07-2017, 12:15 PM
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2002 Mercedes CLK 320
Please, please can you provide document???

Thank you!!!
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Old 06-22-2017, 06:32 PM
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c350
C350 fan problem

Need help.
The fan on my c350 2010 starts up a couple of hours after my car has stopped and it sounds like a jet engine, there's no key in the ignition and the fan ramps up and the ramps back down. This happened on Friday and it eventually run the battery down. I sent it to the Mercedes specialist and he said there were no fault codes and couldn't find a problem with it. Got it back yesterday and drove it Monday for an hour and couple of hours at stand still and it's started up again.
Took it back and he thought it may be the fan and controller. Had this changed along with the battery and again tonight the fan has started running yet.
I'm stumped and would love to know what the problem is and what I can do about it please.
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Old 06-23-2017, 03:18 PM
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not a merc
Make sure the ign voltage stays 0v at the fan controller when the ign is off? Check if there is voltage on ign wire when fan runs when it shouldnt
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Old 01-15-2018, 09:11 AM
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Originally Posted by Russell Ormerod View Post
not difficult to fix.. Do you have star diagnose?
hie russell can you page me on this email...need [email protected]
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Old 01-15-2018, 04:59 PM
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not a merc
Sorry I do not work on opel
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Old 02-12-2019, 02:05 PM
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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.
hi I recently had the same problem started car fan in full speed with or without ac what I did was replace the thermostat and sensor made sure that there was no air inside of circuit then with the car closed also window I disconnected the battery only red waited for at least 15 minutes reconnected the car reset buy it self then I switched ignition on just before cranking press down accelerator for about 10 seconds lift my foot then switch off the car don't remove key then wait for about 2 minutes after star has normal and the car will be completely factory reset that means that is like if you just buy the car
I sort my problem all is running fine
I hope is of some use
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