gnscn

What you say makes sense, but isn't it the ECU that controls the fan? How does a problem with the display engine affect the fan? The indicator shows the error, but since the brain has measured it correctly, it should not start the fan.

gnscn

Thank you. I hope I understand something

CaliBenzDriver

precisely! I am with you on that one.

ECU controls this whole ballgame :

1. the ECT.
2. the fan PWM.
3. the Display gauge.

Your topic matches perfectly with poor ECU GND.
I suggest you clean painted ECU GND at footwell first.

Then research complete GND list (cowl,...) if not fixed.

S-Prihadi

Becareful with OBD dongle which if a slow one.
The more parameters or PID you are reading, the slower the screen update.
So if you have quick glitch, it may not register.
Reduce the data PID to only say 5 PIDs, it will be updated faster.

CaliBenzDriver

this may be a failure mode of the gauge dial itself - Check out this thread of W211 where this defect may be originated.
🤞

gnscn

I went to the electrician. I told him what I experienced and what you shared. After a general check-up, he removed the ECU. He said that there was a problem in some transfer points of the ECU and he fixed it. Something like looseness or lack of contact. I haven't had any problems for 2 days. My problem didn't always show up anyway. So I'll try and check for a while. If there is any development, I will let you know. Thank you for your help.