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Discussion Starter #1
I have 2001 E-320 Station Wagon, recently I am getting Low Coolant message on Instrument Cluster.

Car has been running normal, temperature looks good, also coolant level in reservoir looks fine. I don't see any coolant leak under car or in belly pan. All looks good.

Is there is a chance that coolant level sensor in reservoir is bad?

Please may I get comments and feedback about the coolant level sensor.

Please see attached photos.
 

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Coolant level sensor is magnetic proximity reed switch operated by foam float with magnet inside expansion reservoir. No way to tell which one is bad. Foam float inside reservoir is most likely problem.
 

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Sensor is probably bad. Your coolant is slightly overfilled though. And I notice your engine temperature is slightly low but I don't know how long the engine was running prior to that picture so maybe it was still warming up.
 

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Remove the connector for the ECL sensor.

Measure the sensor resistance at the connector.

If you have a reading between 102 and 120 Ohms, and the fluid level is fine, then the sensor is good. In that case, check the wiring / connectors for opens / shorts.

The windshield washer level sensor (145 - 185 Ohms when fluid level is OK) and coolant sensor are in series and connected to the Instrument cluster directly. The instrument cluster looks for a combined resistance signature between 250 to 300 ohms when both fluid levels are fine. If it sees and open or a short, it will put either washer fluid or coolant level fault.
 

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Remove the connector for the ECL sensor.

Measure the sensor resistance at the connector.

If you have a reading between 102 and 120 Ohms, and the fluid level is fine, then the sensor is good. In that case, check the wiring / connectors for opens / shorts.

The windshield washer level sensor (145 - 185 Ohms when fluid level is OK) and coolant sensor are in series and connected to the Instrument cluster directly. The instrument cluster looks for a combined resistance signature between 250 to 300 ohms when both fluid levels are fine. If it sees and open or a short, it will put either washer fluid or coolant level fault.


Extremely helpful Sir. I'm facing this issue now; sorry to steer off the topic a bit. I have a destroyed windshield washer tank and it's now off the vehicle; I want to connect a resistor, I guess this is the range I'm looking at so it can take away the windshield washer light which comes up all the time. Please advice, what color codes/resistance will you recommend based on your resistance range here? Higher or lower?


Sent from my iPhone using Tapatalk
 

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Discussion Starter #7 (Edited)
All, thank you so much for your support. The issue has been fixed. I did following 2 things.

1. Removed the connector from coolant reservoir level sensor and then plug back in. I pushed it little harder to make sure it is sitting well in connector.
2. My windshield washer fluid reservoir was down to 1/4 level of the both head lamp washing and windshield washing reservoir. I filled the windshield washer and head lamp washer reservoir to top.

Now I don't have any more Coolant Low message on instrument cluster. All good. Car is driving great. I love this W210 station wagon.

In my earlier photos, the coolant level was high because I added little water in coolant to see if this will resolve the issue, but it did not help, so I siphon excessive coolant out of the coolant reservoir.

Also, the temperature when car driving on freeway it stay at 80°C, but when I leave the car parked and running, then it reach just little below 100°C, which is normal.

All good now. Thank you all for your great support. I love this forum and the people who contribute on this forum and support others. Thank you all.
 

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Discussion Starter #8
"Coolant Check Level" Message again. Install New Level Sensor

Hello all I am start to getting again the "Coolant Check Level". I have purchased the new level sensor for coolant expansion tank to replace it. The level sensor was only $10. See Below photos.

Is any one know how to remove the old coolant level sensor? Do you just twist it counter clockwise? Any feedback will be appreciated.

Do I need any O-Ring or any kind of sea?l or new sensor just goes into old sensor spot in coolant expansion tank and there will be not leaks from sensor?
 

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Level switch sits in dry well. I does not make contact with coolant. Brand you have purchased is questionable.:eek
 

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Discussion Starter #10
Witek_M, thank you for your reply. If it is just a dry well then it will be easy for me to just remove electrical connector and first measure the resistance of the existing level sensor which should be between 102 and 120 Ohms. After that I can try this new coolant level sensor.

Dry well means I don't need to drain any coolant from Expansion tank, just get access to coolant level sensor which is quite inward, I will remove the one bolt that is holding the expansion tank and then wiggle the front 2 tabs that are in the frame of car holding expansion tank, once expansion tank is little moving then I will have room to put my hand and do the work on coolant level sensor.

I will keep you all posted.

FYI, I have used URO parts in past, they are not the best, but ok. I have 4 rear windows regulator in W210 replacement with URO windows regulators.

I love my W210's, but the value $$$$ is quite low now, so I just keep them going with parts I can find online or on Amazon.
 

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Discussion Starter #11 (Edited)
Some update. Today I got few minutes to troubleshoot the issue. I connected my Autel MaxiDiag Elite to read what is causing this message on Instrument cluster. I got message that "Short circuit on signal line to the washer fluid level/coolant level sensor" Code B112B.

Just because I did not have enough time today, so just checked the resistance on windshield washer fluid level sensor, it was only 33.6 ohms while the washer reservoir is full.

Then I measure the resistance from connector of washer fluid connector to backward, it was showing 647 ohms.

While the connector to washer fluid unplug, I went into Autel and reset the code. after that I plug it back in.

For now I am not getting message any more on instrument cluster for Coolant Low level.

One question is the washer fluid level sensor with full level in washer fluid of 33.6 ohms is good reading or bad reading? Please someone can comments on it.

Tomorrow I will try to reach to read resistance of coolant expansion tank level sensor.

Thanks in advance for your continues support.
 

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Bad reading. You should get between 145 to 185 ohms at the sensor connector with the cable pulled off for a full tank.

The measurement towards the harness connector, 647 ohms is meaningless, especially if the ignition is on (it carries sense power from the cluster).

You always must make these measurements with the ignition OFF.

You may have some stray resistance on the harness to ground.

Typically you need to remove the connector at the back of the instrument cluster and make a measurement from that connector.
 

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Discussion Starter #15 (Edited)
Bad reading. You should get between 145 to 185 ohms at the sensor connector with the cable pulled off for a full tank.

The measurement towards the harness connector, 647 ohms is meaningless, especially if the ignition is on (it carries sense power from the cluster).

You always must make these measurements with the ignition OFF.

You may have some stray resistance on the harness to ground.

Typically you need to remove the connector at the back of the instrument cluster and make a measurement from that connector.
mrboca, thanks. Since I have cleared the code, all is good, I am not getting any messages on Instrument cluster.

I believe the way system is design is that when IC sees the low resistance in the system, it create code B112B and display on IC the message Coolant Low Level. So look like the logic in instrument cluster is that on low resistance or Mercedes call it short circuit, it will display the message Coolant Level Low.

One other observation is that when I removed the connector from washer fluid level sensor, I was getting no message. It means if there is open circuit, the instrument cluster doesn't display any messages.

Anyhow, all the connectors are connected as normal for washer fluid level sensor and coolant expansion tank level sensor. I have been driving the car and no more message.

When I get some time, I am just going to remove the instrument cluster and quickly read the resistance on IC connector IB terminals 4 and 12. This will give me full loop resistance when Coolant Expansion tank is full and windshield washer reservoir is full also. I will keep you posted.
 

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You probably had an intermittent short on the line which caused the IC to read a short.

I do not think the IC has the capability to display both coolant and the washer fluid low message in case of a short detection on the line, so it displays the washer fluid low message by default, with an error code.

It is also important to note when the actual test is done. In my experience, the washer fluid low message pops up when you turn the contact, and I think it would give implausible value if the test is done when the car is moving due to fluid sloshing in the container. So if you had the fault cleared and then pulled the connector while the key is in position 2, it may not register.
 

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Discussion Starter #17
mrboca, thanks for your reply. As of today, I have not seen any more message on IC for Low coolant level.

I will check the circuit from IC side by removing IC and then taking Ohms reading from Electric bracket B just to see what will be the total loop resistance that goes through coolant lever sensor and washer fluid level sensor.

It is quite difficult to read resistance of Expansion tank coolant level sensor, the connector are way in and unless you remove the air box and then expansion tank, there is no simple way to read the resistance. I will read the resistance of Coolant level sensor via IC electrical connector plus washer fluid level sensor connector per attached IC diagram.

I will keep you posted.

The Washer fluid level sensor is quite low cost, it is sold for only $16.

https://www.ebay.com/itm/153337606533?ul_noapp=true
 

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Discussion Starter #19
mrboca, Thank you so much for such a good info on IC and resistance of individual level sensors and over all loop resistance.

I will remove the IC this weekend and will give you update. I believe I have issue with windshield washer level sensor and NOT Expansion Coolant Tank level sensor.

Again many thanks for your time and support.
 

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Discussion Starter #20
mrboca, some update. Today I removed the IC and measured the whole loop resistance across Expansion coolant tank level sensor and Windshield washer fluid reservoir level sensor. The Reading I got of 154.8 Ohms. Way lower then I expected, but match what you have told me.

My reading of Windshield washer fluid reservoir level = 33.6 ohms

whole loop resistance across Expansion coolant tank level sensor and Windshield washer fluid reservoir level sensor = 154.8 ohms

It means Expansion coolant tank level sensor 154.8 ohms Minus 33.6 ohms = 121 ohms, which is good.

So my problem is the Windshield washer fluid reservoir level sensor, which suppose to be 145-185 ohms and I am getting only 33.6 ohms.

Thank you mrboca, I will get Windshield washer fluid reservoir level sensor for $16.

Below are some photos from today.
 

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