[alpac]

Hi Folks,
Today was a pretty hot day over here, 94 degree. My wife took the 1999 E320 to go downtown. After about 25mns of driving in stop and go traffic the engine coolant symbol came on. She said the car never overheated, the temperature gauge went close to 90 but not more. The engine coolant symbol stayed on until she came back home. As soon as she was home I checked the car and could see that indeed the coolant symbol was on but no engine light. I stoped the car, checked if there was any error code in memory with my OBD2 reader but there was nothing. When I started the car again after only a couple of minutes not running the coolant symbol was gone and never came back even after letting the car iddle for 15mns in hot weather. There is plenty of coolant in the reservoir so it is not a low coolant problem. The fan seems to run fine so I am wondering if there is a sensor somewhere that is sending a wrong message. Any idea?

 

[Kajtek1]

Did you check the windshield washing fluid?

 

[mrboca]

The coolant sensor is located under the coolant expansion tank (plugged into the deep end of the white plastic part of the tank. You may have a flaky sensor, or electrical connection to the sensor. The windshield wiper tank level sensor and the coolant sensor are connected in parallel with different resistor values in series. So it is possible to have a wiring problem to cause a false sensor reading. I would replace the sensor as well as the expansion tank as the plastic of the tank deteriorates in time and develop micro cracks leaking small amounts of coolant.

See the attached for removal and replacement of the tank.

Mercedes-Benz W210 Expansion Tank Replacement (1996-03) E320, E420 | Pelican Parts DIY Maintenance Article

 

[alpac]

Thanks. Last fall I replaced the Coolant Temperature Sensor that is right under the air pump because the previous one was sending an erratic message to the ECM which created a lot of engine hesitation. I did not know there was another coolant sensor under the expension tank. I just came back driving the car and the message came out again very briefly and it actually displays the words "Engine" and "Fan" and the radiator symbol in between the 2 words.

 

[mrboca]

The coolant temp sensor is different from coolant level sensor, but this is not your problem. Once you explained what the warming message is, it is more clear that the fan controller is flaky.

 

[alpac]

Ok so i need to replace the fan controler. Where is it located?

 

[mrboca]

check the link out. it is figure 6. The item is N76.

STAR TekInfo

The pricing (remove the part and make sure you have the right part number that matches in the following link)

http://www.everythingbenz.com/z/part/0255453332-mercedes-radiator-fan-controller-resistor

It could be a loose electrical connection too. Make sure the connector is tight and clean the contacts with electrical connector cleaner, or MAF cleaner.

 

[alpac]

check the link out. it is figure 6. The item is N76.

STAR TekInfo

The pricing (remove the part and make sure you have the right part number that matches in the following link)

Mercedes A 0255453332 Radiator Fan Controller/Resistor

It could be a loose electrical connection too. Make sure the connector is tight and clean the contacts with electrical connector cleaner, or MAF cleaner.

Excellent. I wil start with checking the connections. THANKS

 

[alpac]

The diagram is pretty difficult to read even when magnified. Also I looked at the photo of the part on amazon and tried to find the same part in my car around the fan but could not. Is the Auxiliary Fan Control Unit located inside that black cover at the center of the fan like the diagram seems to indicate?

 

[mrboca]

You could also check the fan operation by pressing BOTH AUTO buttons on the a/c control units simultaneously for 15 to 20 seconds. The fan should turn on at the highest speed.

The fan module on your E320 is mounted under the car at the left front frame rail.

If you had a MB scanner or equivalent, you could have exercised the fan unit at different speeds selectively.

And the tip for getting a better picture is to click on the "printable version" button at the right top of the diagrams. You will have the PDF version which is clearer.

 

[alpac]

And the tip for getting a better picture is to click on the "printable version" button at the right top of the diagrams. You will have the PDF version which is clearer.

Ah! ok. Mrboca you rock. Big thanks again for your help.

 

[illstplaya]

The module is behind the front bumper. It's easiest to see if you remove the plastic cover shields at the bottom of the engine. You will see it much easier this way. Those diagrams don't really tell you exactly where to look. It's just giving you a general location. I would take a picture of my car to show you the location but I'm not at home.

You can see it if you look at it from a top view, looking down but it's difficult and there's not a lot of room to work with. If you stand at the front of the car and look into the engine bay, you need to look underneath the right headlight housing, then look even further right and you should see it.

This is what you are looking for.

 

[alpac]

Thanks again folks. I will look at this sometime this week after work an will report back. I am booked all day tomorrow for the baby shower of my first grand child. Jeez!! I feel too young to be a grand dad

 

[mrboca]

Congratulations Grand dad

 

[alpac]

Today I unplugged the fan controler unit that is under the driver side headlight and sprayed contact cleaner. I also checked the wiring and it does not look damaged although it is wrapped under a plastic cover so if the wire was bad underneath I would not see. Anyway I plugged everything back and went for a 30mn ride in hot weather and I did not get the error message. Since the message appreared randomely before I will have to drive the car for for sometime with no message to claim victory. From what I could see of the fan control unit from underneath the car replacing it will need to remove the front bumper so as to reach the screws that hold it.
Thanks again for your help in locating this module.

 

[alpac]

Today after 25mns of driving and a 5mns stop at a shop the message came back within 2mns after I took the car back. Back at home I checked the radiator fan operation by pressing both "auto" buttons on the a/c for about 15sec and indeed the radiator fan speed increased quite a bit but that also triggered the message to be displayed. I turned off the engine then started it back and the message was gone but when I pressed the 'auto' buttons for 15sec that again triggered the message to be displayed as well as the fan speed to increase. So what seems to happen is that everytime the fan is instructed by the controler to go full speed it also triggers the message. Do you still think this is a controler issue or a fan issue? I am thinking that the fan either works or does not and it does work in my case. So that leaves the fan controler to be faulty or a bad wiring, right?

 

[mrboca]

When you start the car with engine cool the fan should not turn at all (ECT < 70 degrees C and a/c off). As the engine starts warming up the fan gains speed up to the full speed. If you observe the variable fan speed behavior, the fan should be fine. As far as I can see there is nothing that monitors the speed of the fan for your car (2 wires from the controller to the fan). There are some fan versions that the fan rpm is monitored and and a fault is generated if the fan rpm doe not meet the spec., however, I do not think yours is one of them.

Have you checked the fault codes with a scanner ? There is a P0801 code regarding the suction fan controller, but I am not sure how the SAM unit detects the fan / fan controller issue, or whether it applies to our cars. Maybe when the fan is turned on to a full blast the SAM unit checks the PWM line voltage level which should be at ground level. Unfortunately I do not have access to the internal logic of the SAM.

You can try your scanner, or if you have an access to a scanner like MB Star, it would make the diagnosis much simpler, as you can read the internal codes from the SAM and the ECU, and also test the fan unit at various operational stages. My car has fans in the font of the radiator, so it is different from your car's single electrical fan. With my scanner, I could check the fan speed in percentage, and who requested the fan operation (engine coolant temp, or a/c). I can turn the fan on at different speeds so I can test the controller and the fan.

I tend to agree with you, based on what you are posting the wiring or the fan controller are the main suspects. To some degree there may be a problem with the SAM but it is difficult to diagnose this without the SDS or equivalent.

Do you observe the coolant temperature at the instrument panel or the a/c controller menu display ?

 

[alpac]

mrboca, thanks again for your usual very detailed answers. There is no code rendered that I can read with my generic scanner. Unfortunatly I dont ahve the MB Star scanner but I may need to invest on one now that I have 4 different Benz's. The fan indeed does not turn when the car is cold and starts turning after the car gets warmer and I dont get this message right away. As I said in my previous post it looks like I get the message only when the fan is supposed to go full speed. I will start by better inspecting the wiring and then if nothing found I will replace the controler.

 

[alpac]

I am reviving this thread that I started several months ago. I never took the time to replace the fan controler that was possibly the cause of my Engine fan message displayed on the dash and whihc made me start this thread. Beside displaying the message when the car was hot and when the radiator fan was running at max the car never overheated and ran fine until now. Since yesterday though additional symptoms have appeared which I am wondering if they could be linked to the same cause that is to say a failing fan controler. For a couple days now the Engine fan message appears everytime the AC starts. As before the car never overheat and tmep stays always in between the 80 and 90 marks when hot. Today my step daughter was driving the car and she said she turned the AC on which triggered the Engine fan message on the dash and then the car stalled. She tried to start the car again the car would crank but would not start. She tried to start the car 10mns later and the car started and she was able to come back home. There is no error code in memory that my standard OBD2 reader can find. Beside the engine fan message coming on and the AC not blowing cold the car runs fine for now. One of my next move is going to be to replace the fan controler. I am not sure if the engine fan message issue and the car stalling today are related to the same fan controler problem or if they are 2 different issues. Of course the problem with the engine stopping when hot and not starting again after 10 mns make me think of the infamous cranshaft position sensor issue although it had already been replaced back 50kmiles and 5 years ago. I would think that a CPS issue would render an error code would it not? I appreciate idea or any though you folks may have about this.
Thanks

 

[mrboca]

I believe they are not two directly related issues. The stalling sounds like the CPS issue, and the CPS issue is engine heat related.

The fan error is more like the fan issue from what you are describing. The fan motors get old and tired, and do not properly respond to higher speed requests when the brushes get worn out.

I believe there is a monitoring function of the current based on the fan speed level. Higher the speed higher the current demand. So when the AUTO keys are pressed you are asking the fan to turn at maximum speed, which is probably not attained due to worn brushes.

Try driving with the EC button on the a/c controller lit (compressor off) or turn off the a/c by pressing the - button, and see if you are getting any fan errors at all. The fan speeds due to engine coolant temp are generally in stage 1 and 2 (low speed) unless you have overheating problem with the coolant.