Rev counter malfuncion w209 270cdi
 

Hello, MBWorld! A few hours ago this happened: I started the engine for the 1st time in 20+ hours and the rev counter stood at around 100 RPM. I noticed it about 2-3 mins into the trip. It was revving up when accelerating then it dropped to the same low values. Everything worked fine - AC (no impact on revs) no weird sound, everything was as usual, perfect acceleration, shifts, no weird noises, nothing. I am sure the car was working at regular revs. The only abnormal thing was the arrow being at around 100 rpm as shown in the picture. After about 7-8km of driving i stopped and turned off the car, restarted it immediately and it was perfectly fine with revs around 800 as usual. No real issues, just felt weird. No malfunction messages, everything is alright. All I know as a possible cause is that I had stopped at a slightly bent parking spot, about 30 degrees bent on the right hand side. Nothing else comes to mind. I'd love to know what someone with more experience thinks about this.https://cimg8.ibsrv.net/gimg/www.mbw...5839891a9.jpeg

My guess is that it's an issue in the instrument cluster. Since it seems OK now, just chock it up to "electrical gremlins".

I just drove it again, worked flawlessly. I wonder what might have caused it but I'm happy there's nothing huge going on. All my friends say ' if there is a problem the boardcomp would know, no malfunction - no worries' .
I think I just drive on and forget it. @Rudeney I am unaware of the 'electrical gremlins' , sorry I'm still MB noob :P

So an update: Everything was working yesterday, today I start the car, the rev counter stays dead at 0. No other issues, the car runs fine. I called my mechanic and he told me not to worry and that I can drive safely, almost certainly it is the arrow being broken, nothing serious. No malfunctions, etc. Easter is this weekend I wont me able to fix it immediately. Anyone else had this issue? Any possible tricks I can try to fix it ? Thanks!

Aaaand out of the blue it works right now... WTF?!?!

After series of tests I concluded that the rev counter doesn’t work at start, when the car is cold. Then after about a minute the rev counter starts to move but doesn’t show the real values. At this point if I restart the car the rev counter works fine. What should I do? It feels weird but kinda non issue, I really don’t know...

Sounds like a bad instrument cluster. Given the high cost to have it replaced, I'd just live with it. There are some electronics shops here that do repair them, but since you are not in the USA, I can;t recommend one.

It has worked for the last 2 days, I think If i keep the key on pos 2 longer it works, just thoughts though. I can live with it, thanks for the responses. A member of the local MB community said it could be due to faking the mileage - they did it badly. I am from Bulgaria and things here are a bit odd :P Thanks Rodney! I will write here if there is more info or update on the case, something like a log of the events. Good luck!