300SDL Instrument Cluster Erratic Behavior - PeachParts Mercedes-Benz Forum

300sdlguy · #1 08-26-2012, 08:18 PM

I took out the properly working cluster on one of my 300SDL's to refresh the needles on the gauges. At some point the cluster has been out prior to my ownership as the main plug connector was broken (glued it back in properly).

When I connected the cluster back in, there is a definite problem. When the key is put into the on position, the oil pressure seems to be getting the fuel readings, the temp gauge the oil pressure and the fuel gauge shows empty with reserve light illuminated. Initially when I turned the key on, the speedometer was getting power and registered 20 mph.

I took another working cluster from another 300SDL I have and it does the same things when connected!

Anyone have a clue what is going on, and exactly where I need to look to resolve this problem?

Hit Man X · #2 08-26-2012, 08:23 PM

Good to see your are alive!

Maybe you have a weak ground?

sixto · #3 08-26-2012, 09:54 PM

The round connector has a central post with a flat edge that should be clocked to fit a corresponding slot in the gauge board. It's a weakness in the design that you can partially engage the connector when it's not in the correct orientation. However, it's unlikely you could have mis-clocked the connector exactly the same way twice.

Sixto
87 300D

300sdlguy · #4 08-27-2012, 01:54 AM

I AM alive !!!!

Yes, I am sure its connecting as it should, repaired the broken post myself to ensure there wouldn't be an issue. I am not sure what could have happened between taking it off and reinstalling it?!?!

Which ground HitmanX(Eric)? Ground to cluster or?

Also, it appears that there is no illumination now, but its been so long since checked that, not sure that is a new issue, but just in-case that is a clue to anything.

Clemson88 · #5 08-27-2012, 01:17 PM

I might be the worst at these cluster so take this for what it's worth.

Find the ground pin on your cluster. Find the ground pin on your round plug. Make sure you have them matched up when you put them together. No insult intended but pluggin it up wrong would certainly yield problems such as you've described.

Did you disassemble the harness plug at anytime?

foolio · #6 08-27-2012, 05:58 PM

Do you disconnect the battery to do the R&R? I have heard that not doing that can toast a cluster pretty easy. No personal experience.

300sdlguy · #7 08-29-2012, 04:43 PM

Never insulted, when advice is given in a constructive manner! It does seem as if its connected incorrectly, but I have checked and double checked, might be time to triple check.

I did NOT disconnect the battery, hadn't heard of any issue with the clusters if batt is still connected on the w126's.

When I put the cluster into another 300SDL it works correctly, so it appears some connection and/or ground OR something else is wrong with the other 300SDL, I just don't know where to start.

Clemson88 · #8 08-30-2012, 09:50 AM

Did you disassemble the plug with the "D," shaped thing in it's center?

I've taken a few plugs apart and always flip them over and get a picture of the location of the wires. Sometime, I get confused because they are upside down or backward but they usually go back together correctly.

Perhaps with the work you've done on that plug you may want to take another look inside it.

I know it sounds a little insulting but when I get frustrated and confused I just have to mentally outline my plan and take it one step at a time.

300sdlguy · #9 08-30-2012, 03:34 PM

I hadn't taken apart the connector/plug, the only thing that I had done was glue the "D" pack into place into the exact position if was broken off from. But it sure does sound like something is up with the connector, but I have inspected it as best I could without actually taking it apart.

Clemson88 · #10 09-01-2012, 03:29 PM

ON THE CLUSTER:
To find the ground pin on your cluster put one of your tester's leads on the ground of the speedo sub-cluster. That is a plate between the fuel, temp, oil sub-cluster and the speedo cluster. The screw on the lower-right goes through it for it is attached to the speedo cluster and sandwiched between the two cluster assemblies.

Touch the other lead to each of the pins on the fuel, temp oil cluster. Only one should give you 'tone.' That'll be your ground pin. Mark it!

ON THE PLUG'S GROUND:

Find a place on your driver's door hinge and clean off a spot to insure you have contact. It's wise to check this by making or picking two spots to make sure you can get 'tone,' with your tester. You might want to take that lead to the negative post on the car's battery.

Put one of your tester's leads on that spot and touch/insert the other lead into the plug's holes. When you get 'tone,' mark that spot.

Make sure your marks line up when you reconnect the cluster to the wiring plug.

If you lift the wiring plug and wire up and pull a little you can get that sucker to come out just enough to make the connection while holding the cluster on the (DS) left side of your steering wheel with the back exposed enough to actually see what you are doing. The wire length will allow you to move the cluster over the wheel and work it in on the other side.

Don't get in a hurry. MBZ's can smell frustration, fear and panic. Just tell the car you own the title and make it behave. As said before, no offense intended.

Luck and let us know how this turns out!

300sdlguy · #11 09-08-2012, 02:28 PM

Thank you so much for the write-up! Unfortunately, I am not sure which screw on the lower right, as I am looking at the cluster from the back, you are speaking of. Is it the one just above the dimmer switch assembly? I have attached a picture of the back of mine.