tmelbye

Hello world,

I’m having an issue with cooling fan on my W212 2011 Diesel Avantgard.

When turning of the car the cooling fan start blowing full force and will not stop until the battery is dead.
The car has been sitting idle for a while now because I got tired of it.

Now I started going again and I think I’m getting closer.

I checked earth, fuse MR4 and fuse 22, all checks out.

I probe the plug connected to the fan and get the following signal:

1 BRN Earth – OK

2 RED from fuse MR4 – OK 12v

3 BLK/RED from front SAM – OK 12v

4 GRN/BLU from ME-SFI (have no idea what that is) – Nothing…

I suspect there is an issue with the last cable as it has no signal.
Not even sure if its supposed to have any. (that’s why Im asking)

As I’m unsure of where the ME plug is I haven’t been able to check for continuity.
If I can find the correct cable and get a signal, I could replace that single cable instead of replacing the whole harness.



I have Macgyvered a temporary solution that is easy to restore to original.

From MR4 I run 12v to a 100a relay. This relay gets signal from the fusebox so it cuts power to the fan as the ignition is turned off. No cables cut so its easy to revert.



Any ideas?

S-Prihadi

If your engine model and variant is the same as this link, use the wiring diagram : https://mbworld.org/forums/e-class-w...ml#post8879691
Avoid using NON MB wiring diagram. Most aftermarket wiring diag for MB is not good.


OP wrote :
4 GRN/BLU from ME-SFI (have no idea what that is) – Nothing…

I suspect there is an issue with the last cable as it has no signal.
Not even sure if its supposed to have any. (that’s why Im asking)

That no 4 is a LUES label at ECM wiring, it is a PWM ( use Duty cycle in your DMM ) signal for fan controller to perform the speed required.
10% Duty cycle PWM means FAN IS OFF
90% means fan is to run MAXIMUM
No duty cycle at all is an ERROR state and the fan will do maximum speed. So if #4 wire got broken, engine does not overheat as fan will go maximum.
100% duty cycle also an ERROR state because that is non PWM signal, it is just complete contact, so FAN would do maximum speed too.

There are cases the Engine Computer is the bad dude, missing that LUES signal.
I hope yours is not the ECM being the bad dude.

tmelbye

Thanks for your answer.

Do you know which connector I need to check to find that cable?
if I can measure continuity I would be able to determine if the fault is in the cable or the ecu.

CaliBenzDriver

Allow me to suggest you scan this intelligent car...
You don't want to ignore what sensor the ECU maybe trying to act on.
​​​​​​

S-Prihadi

Use MB vin code decoder, get a data card. With that we get your engine and tranny actual model number and the 3 last digit variant....and also super important the options
the engine has, which is required to use the wiring diagram because MB packs the wiring diagram with so much options, thus you need to "clean" the wiring diagram to suit
your engine.

I don't even know your engine model+variant, how can I answer your question ? I am totally not familiar with MB diesel engine too,

If you have faith that the current 3rd party wiring diagram you are using is correct, the answer is there already.



Your engine footnote 1 and 2 in that small circle.
If your engine is a 1, that means the pin at the ECM is to be #43 .
if your engine is a 2, that means the pin at the ECM is to be #44 .

But I then asked, which connector is this diagram referring to ? F or M ?
ECM has two connectors, one is called M and the other is called F. One is up to 58 pins and the other is up to 96 pins.
But I see the letter M above the circled 1 and 2, so M is the connector ID

There is a label at the connector plastic body to tell which is M and F.
But again..... I do not know your engine model and variant to verify if the 3rd party diagram you are using is CORRECT or not, compared to MB original wiring diagram.

tmelbye

Here is what I found about the carWDD2120021A398xxx

E 220 CDI / D

R4-DIESEL ENGINE M651

DISPLACEMENT 2.2 LITER

I was checking today and thought about what you said about 10% on standby.
got a better multimeter and found that the pin had 1.2 volt with ignition on (2nd)

was reading error codes and got P0480 after running the car without fan connected.
after erasing code, plugged in fan, running car for 5 minutes it came out clean.

Bypassed my McGyver fix so the fan had constant 12v as original.
Was testing and everything was looking normal
Even when I turned of the ignition and removed the key.
Suspecting it could be a bad connection that fixed itself when I was tinkering around I planned to keep it connected for a while to see.

All good.
Until I removed the OBD reader….
The fan started going for full.

What the fugg……

Begining to suspect faulty ECU/ME or fan controller.

S-Prihadi

well in theory but not always true.......... a regular DMM not able to read duty cycle in %, and when is using VOLT selection to read a 10% PWM signal,
could show 1.2 volt or 10% of 12V.

tmelbye

Found a video on YT showing how to check the fan and the PWM signal is possible to read with a standard multimeter as % of 12v.

Unfortunately I only have Delphi software, so I don’t have all the options to run different functions like cooling fan.

But its kind of interesting that the fan started running full the second I pulled the OBD2 device.

​​​​​​​I’m getting more and more confused.

Guess I should find someone with xentry that could do a deep dive.