Help! Help! Instrument cluster does not function anymore - PeachParts Mercedes-Benz Forum

Texholdem · #1 03-08-2009, 02:58 PM

The history: because my instrument cluster (IC) had a few blind dots in the display of mileage, clock and outside temperature I tried to repair it with the result that all dots have gone dead. All the needles of the gauges for engine temperature, fuel, speed and rpm still worked fine.
I then replaced it with a used instrument cluster bought on ebay. The new one has no blind dots but all the needles of the gauges for engine temperature, fuel, speed and rpm are inactive, they do not move as you can see in the video at

http://s245.photobucket.com/albums/g...entCluster.flv

which I recorded during a test drive.

I thought the new one might be defective regarding the dial needles and deployed my old one again because better to have all blind dots than no information on speed, engine temparature and fuel gauge.

To my great surprise they are now dead on the own one as well.

My guess is that the malfunction of the dials is now not from the cluster, since it fails on both clusters.

I replaced all the related fuses #4, #6 and #7 from the fuse box under the hood.

Please tell me what could it be that no dial needle moves?

Texholdem · #2 03-09-2009, 01:14 AM

New development: The game below was played upon me 3x this afternoon and evening. In regular interval I started the engine just to check and lo and behold all needles came to life except for speed because the car did not move. Engine temparature went above 40, fuel gauge to almost full (I filled up 30 miles ago) and rmp went up when I pressed the gas pedal.
I wanted to be sure, shut down the engine and restarted ...
The dial needles are all dead again and again after another and another trials.
There might be something like loose contact, since the cluster itself works fine, but what?
Help! Help! Help! I'd appreciate all comments!

Arthur Dalton · #3 03-09-2009, 02:15 AM

Looks like a poor ground...........
Is ABS lamp ON ?

Texholdem · #4 03-09-2009, 02:26 AM

No, ABS is not on, and no sign of other problems. I pulled the codes and there was none.

How can I check the grounding?

Thanks!

Texholdem · #5 03-09-2009, 02:37 AM

Good night Mr. Dalton!

Arthur Dalton · #6 03-09-2009, 02:37 AM

Well, not sure which is ground on that chassis, but if you can see a possible ground connector, bring jumper over there from bat neg- and see if that makes the circuit... I don't have that schematic.

Texholdem · #7 03-09-2009, 09:31 PM

I tested the ground on the circuit board while the cluster is fully connected and can see good ground, since all other functions of the cluster work fine (lamps for headlight, direction lights, the whole signals when turning the key to position 2 etc..) except the needles.

If I leave the car for some hours then the first time I start the engine, the needles come to life then dead again at the next trial (turn engine off and restart) without me touching anything, the game can be repeated after several hours again and again.

I reached behind the cluster, wiggled the harnesses to see if there is anything loose with no success.
I make sure that the plugs connected to the cluster are firmly inserted; same situation.

Someone suggested that the relay unit K40 could be the cause. Mr Dalton, do you share that opinion? Is the K40 positively linked to this defect? If yes I can buy a new one.

Thanks for being patient with me.