cooling fluid lamp on + electric fan no function

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c200 classic -98 with 280000km

The cooling fluid is on as soon as I start the engine, the level is fine and no air is trapped in the system. Also, the electric fan does not kick in so the car overheats if im stuck in traffic etc. Before the fan was always on when the car was, and later it was on even if I turned off the car - so I had to unplug it to avoid draining the battery.

I checked the cooling fluid sensor and window washer sensor got these values, are they correct?

Cooling fluid sensor: 110 ohms
WW fluid sensor: 173 ohms

Did check the electric fan control unit that is located by the driver side wheel well and when I opened it components were blown, circuit was damaged and everything was corroded as hell. So I bought a new control unit, replaced it hoping it would solve both the cooling fluid lamp and the fan problem, but nothing.. Where do I go from here?
 

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You can check for moisture under the SAM in the fuse box.

There is also a fan fuse.

The switches in the water and washers are only switches, and should read 0 ohms in one direction, and open circuit in the other
 
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What is the SAM? Is it the fusebox on the driver side that is closest to the windshield, the one you need a screwdriver to open?

Will check for a fan fuse.

How do you mean they should read 0 in one, and open in the other? Sorry don't follow, how should I test this?

I drove the car today with the new fan control box, and the cooling level light went off! Min you this has not happened for the last two years, it has always been on never going off. But now, it comes on when I start the engine, and goes off after 1-3 minutes and stays off almost all the time. It sometimes illuminates for a minute or two and goes off again. Did not test the fan since the temperature was ~80C.
 

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What is the SAM? Is it the fusebox on the driver side that is closest to the windshield, the one you need a screwdriver to open?

Will check for a fan fuse.

How do you mean they should read 0 in one, and open in the other? Sorry don't follow, how should I test this?

I drove the car today with the new fan control box, and the cooling level light went off! Min you this has not happened for the last two years, it has always been on never going off. But now, it comes on when I start the engine, and goes off after 1-3 minutes and stays off almost all the time. It sometimes illuminates for a minute or two and goes off again. Did not test the fan since the temperature was ~80C.

The SAM is the ECU in the fuse box with 2 lids.

Re the switches in the water top up tank, they should have no resistance when they are closed, that is zero ohms
 
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Thanks for the tip, will check it out and reply with the results!
 
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The SAM seamed fine to my visual inspection

Checked out the fuse/relay box on driver side next to the windshield. All fuses were ok and the relays seamed fine, no sign of oxidation moist etc. The only problem I found was the green relay, when I shake on it it sounds like something is loose inside and looking at the pics below it looks like moist/dirt/oxidation.

Also, that green relay is supposed to control the fan HI setting? Because, now the coolant level light is almost always off, but every time I turn on AC full blast, the light illuminates within 30 seconds and the fan does not kick in. Safe to say that this relay is causing it? Can I test the relay with a multimeter?

Its a SIEMENS with nr 002 542 03 19

http://public.openmindedprojects.com/bil/IMG_1062.JPG
http://public.openmindedprojects.com/bil/IMG_1063.JPG
http://public.openmindedprojects.com/bil/IMG_1064.JPG
 

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Fans do draw a high current, hence the need for a relay, it would not be expensive. I cant be 100% certain, but it would be a good move to change it
 
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Changed it today, was about $10 and the new one also sounds like something is loose inside when you shake it - so I guess it is normal.

Too bad it didn't resolve my problem, everything remains the same. But I do notice something - when the car is below 80 degrees C, the coolant light stays off, unless I turn on the AC - then it comes on and goes of in ~1 min after I turn off the AC. But when the car gets a bit warmer 82-85 C, the light comes on and goes off, randomly it seems..

Is there a way to check that the fan is working, connecting it to a power source?

Also, I had the ignition on but the car off and I disconnected the temp sensor on the engine (right in front of the fan) but nothing happened, is the fan supposed to turn on in this situation? You could hear the water pump and the air condition fans turning but that was it..
 

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>>the engine fan cuts in to full power at 80c

Where's the 80C measured?
 

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The engine fan is a visco coupled fan, that is a coupling that is operated by a by metal strip that cuts the fan in at 80c.

The electric fans do not come on until 100c, it think that the sensor that you tested was the water temp gauge sensor, the electric fans uses a thermal switch.

I will try and find the exact position of it but it takes much searching
 

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My 1999 C200 doesn't have a viscous fan..(!)

We have 3 quite major differences that can give problems, 94-mid97, then 97 to mid 99 and 99 on to the end of the run

It makes searching and advice hard when you do not have the car in front of you
 
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What a nice clean engine you have :shock: and no engine fan,, I will have to look it up tonight
 
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Thank you will be waiting for your reply!

Hehe thank you, I try to clean the engine bay a couple of times / year. You should see the interior, 11 years and 280000km later and it looks feels and smells like new. Some people would call me strange ;)
 

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Once again there are 3 versions of the fans,

The early cars >97 the fan cuts in at 103ºc and off at 100ºc, cars >99 with the 2 stage fans come on in stage 1 at 107ºc and off at 100ºc, and stage 2 on at 115ºc and off at 107ºc.
99 on use an electronic fan controller with variable speeds and no figures for this
 
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Ok I see, I don't think my temp is near 103 C when the light comes on, unless my temp gauge is off by 20C.

Will hook the fan up to a 12v source and see if the fan is working. Don't know where to go from here, maybe a shop to read fault codes?
 

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