EnDLeSs_27

For some reason I keep getting the Coolant Check Level error on my Mercedes.

I have a 2002 c230k. I did a complete flush of the coolant to try and get rid of the error but that did not help. I also changed one of the sensors located underneath and outside of the tank (thought maybe it was a faulty sensor). That did not work either. The coolant tank has the correct level of coolant but the error keeps popping up.

Does anyone know of any solutions to this problem?

ontmiss

https://mbworld.org/forums/c-class-w...ar-6m-old.html

https://mbworld.org/forums/c-class-w...t-message.html

LILBENZ230

This happens on the older C-class when the washer fluid level is low. Check that.

EnDLeSs_27

The washer fluid is full as well. I just checked that.

However, Now I am getting the Washer fluid level check error and Coolant level check.

I am getting an error for both my washer fluid and coolant level. The washer fluid is completely full. Just like I mentioned in my first post, my coolant was completly flushed out and a new sensor was replaced underneath the coolant reservoir tank.

Any more ideas?

ontmiss

Washer fluid canister has also level switch/sensor, could be that one is gone.

EnDLeSs_27

Do you know exactly where the sensor is on the washer fluid reservoir? Is it the switch next to the pump?

And if that sensor has gone bad, would that mean the reservoir tank needs replacing? Or is there a small part that I can buy. Please give me the part #'s

ontmiss

Have no idea what's part #. See attachment, there is 2 of them, one in washer and another one in coolant reservoir

tommy

It's the same sensor for both.

Did you replace the right sensor? If so, maybe that sensor was bad as well. That's the only thing I can come up with other than more serious electrical trouble, which I doubt, even for a Benz.

EnDLeSs_27

The only sensor I replaced was the "coolant level sensor" I purchased from

http://www.autohausaz.com/search/pro...Level%20Sensor

This was after a coolant flush. Yet the Check Coolant light remained on. After a while the windshield washer fluid light came on. I checked that, and the tank is full. So I am assuming there must be another sensor in the windshield tank and that is definitely bad.

This is probably the sensor that is inside the windshield tank.

http://www.partsgeek.com/gbproducts/...ek+Google+Base

Any more comments on how I should proceed?

tommy

Ok, we're using the term "sensor" for two different things. You're talking about the physical sensor that detects the level of the fluids, while I am talking about the sensor that sends the electrical impulse that one of the fluids is low (look to the schematic that someone posted on this thread; they're hooked in series, not parallel, so when one trips up the circuit, the warning goes off, but you don't know which one it actually is).

My guess is that you're barking up the wrong tree, and it's the sending unit for the message, not the physical float in either tank, that needs replacement, as mine did.

EnDLeSs_27

So this isn't something a DIY'er can do and that I will have to take it to the dealership to get it fixed?

ontmiss

I beleive that one from partsgeek will solve the problem since you already changed another one. You can easy test it by unpluging and shortcut connector.

EnDLeSs_27

Just an update. I changed the windshield washer tank sensor with the partsgeek link I posted earlier and my problems were solved.

BOTH "Check coolant level" And the windshield washer fluid level error went away.

So if anyone else is experiencing this issue. You should first change the coolant sensor if that doesn't fix it. Then change the windshield washer sensor.

Glyn M Ruck

+1

mtnman82

Interesting... I'm getting an intermittent 'check coolant level' message but my coolant level as well as windshield fluid level are both fine. I guess these sensors have a very finite lifespan.

So there's a separate message for the windshiled fluid level??? I wonder how the car knows, if both sensors are in series?

ontmiss

Same as many things in modern cars. One wire can carry lots of different signals. Imagine you connect 12V trough 2 switches then to computer. Computer is getting 12V what means everything is OK. Now winshield level goes down what transfer current through resistor in switch and computer is getting 7V what register as low winshield fluid and show you on display. Now there is another lets say higher resistor in coolant level switch and when current pass through that one gives 5V to computer.

Think abouth computer keyboard, USB connector with 4 wires, 2 of them are power and 2 are for data, so how computer recognize all those different keys through only 2 wires.

mtnman82

Yep, I'm very aware of serial communication links in our world (keyboards, USB, SATA, rs-232/422, CAN, I2C, etc. etc.) but didn' think these sensors were that smart. I was thinking they were just simple switches (i.e. open or closed) based on another post suggesting jumpering the sensor plug to determine if it was faulty or not. So these sensors don't 'open' (or 'close') all the way - there's a resistor in them? And you believe the electronics are measuring a voltage or current through the sensors? Or as above, Tommy mentions what I'd call a control unit for sending out 'impulses' (i.e communications) to the sensors?

ontmiss

Looks like both of them have resistor inside. Check ATT., S41 is Coolan Sensor Level, S42 is Windshield Level Sensor. Page 4&5.

EnDLeSs_27

Ya if your coolant and windshield fluid levels are fine then your sensor went bad.

Same thing happened to me, so I replaced both the sensors ~$10 for coolant sensor and ~$16 for the windshield sensor. As soon as I connected the windshield sensor both errors went away.

I'll take some pictures of the sensor locations if you need some help.

mtnman82

pics are always awesome and usually a time saver - thanks!!!

EnDLeSs_27

Forgot to check this thread

Here are the pictures. This is only for the coolant level sensor. It is located under the tank. Unplug it than turn the sensor 45 degrees or so and it will come loose.

I did not take pictures of the Windshield washer sensor. But if you remove the "panel" by your tire you gain access to the windshield washer tank. The sensor is located on the right side slightly above the pumps. You will have to pull this sensor out from the tank. So if your tank is full of fluid it will spill all over the place. So be prepared.