Jumping Guages - Page 2 - PeachParts Mercedes-Benz Forum

bbeardb · #16 04-24-2006, 11:33 AM

My speedo is controlled elctronically. I was surprised to see that when I pulled the cluster out.

Edit: I think my oil pressure guage was elctronic as well.

SD Blue · #17 04-24-2006, 11:45 AM

Yes, on the W126 all of the guages, including the speedo and oil pressure, are electronic.

Also, if I recall correctly, nearly all of my guages had spasms with the loose engine-chassis ground. I think this was due to where instrument power comes from.

BTW, the ground strap itself was not loose, the exhaust bracket it was attached to was. It eventually became bad enough to cause intermittent starting problems.

bbeardb · #18 04-24-2006, 11:55 AM

Quote:

Originally Posted by SD Blue

Also, if I recall correctly, nearly all of my guages had spasms with the loose engine-chassis ground. I think this was due to where instrument power comes from.

That's probably not my problem then as only the temp guage and fuel guage jump sometimes (temp much more often than fuel). It still can't hurt to check though.

pberku · #19 04-24-2006, 12:11 PM

I am currently dealing with a similar problem with my temperature gauge. The cluster was removed recently to replace the outside temperature sensor, and a few days later my coolant temperature gauge decided to develop a delay. Basically I have to whack the instrument cluster to get it going. Once it does it stays working till I turn the engine off and on again. Most of the time it gets going on its own after about a 20 Second initial delay.

I checked the main connector at the back of the cluster and its seems to be on properly. But thats as far as I got. I'll wait till the problem gets either better or worse before I deal with it again.

barry123400 · #20 04-24-2006, 12:52 PM

Sorry for the misinformation. Thought he had a 123 with the mechanical speedo and possible oil pressure direct feed pressure line. Will look a little more carefully before I jump next time.

Pete Burton · #21 04-24-2006, 03:38 PM

Quote:

Originally Posted by barry123400

Your oil pressure gauge is not electrical so it cannot be affected by electrical problems I believe. The speedometer is the same and operates by mechanical function. Do not forget it is a very common problem to have a bouncy gas gauge in this model. But certainly not usual to have a jittery heat gauge. For the short time it really requires doing the grounds is sound information.

The oil pressure gage IS electrical on the SD.

tobybul · #22 11-27-2010, 08:05 AM

I realize this is an old thread but just wondered if bbeardb ever figured this out.

andrewtexas123 · #23 11-27-2010, 10:34 AM

What's the best way to clean grounds and fuse connections?

#24 11-27-2010, 11:14 AM

I fixed the jumpy gauge problem on my 240D by adding a separate ground wire from the metal part of the instrument cluster to a ground point under the dash.

tobybul · #25 11-27-2010, 04:10 PM

Quote:

Originally Posted by Craig

I fixed the jumpy gauge problem on my 240D by adding a separate ground wire from the metal part of the instrument cluster to a ground point under the dash.

Thanks, Craig. I guess I was more curious as to what caused the jumpy gages. After looking closely at the ckt board, I found that the ground ckt broke. Its the ckt that goes to pin #15 of the 15-pin connector. #15 is the ground.

Lesson learned: Whenever messing with anything electrical with the car - always disconnect the battery first. I remember way back shorting the terminal going to the clock as I was connecting or disconnecting the cluster. After that, the gages were jumpy. Only now did I notice the ground ckt of the board burned.

The board ckts do not have high ampacity so I can see how this would happen. Obviously less than the smallest fuse so the board ckt acted like a fuse.

So, I am doing the same thing you did - running a separate gound which should accomplish the same thing. I was going to resolder the ckt but its difficult to get to where it broke.

bbeardb · #26 11-27-2010, 05:49 PM

Quote:

Originally Posted by tobybul

I realize this is an old thread but just wondered if bbeardb ever figured this out.

No, I never did. If the new ground works for you, let me know. I'd be curious.

ImBroke · #27 11-27-2010, 06:16 PM

Mine was a burnt solder trace on the back of the gauge cluster. How's your cluster look?

tobybul · #28 11-27-2010, 10:16 PM

I did run a separate ground wire from the cluster ground to the chassis and that resolved the issue.

The reason the gages got jumpy or bouncy is that they lost their ground. From a suggestion from another member, I closely examined the ckt board where the fuel gage is and traced the problem to an open ground ckt. Mine was on the ground ckt that connects to pin #15.

I wanted to jump it with solder but it was tricky to reach. Running a separate ground does the job.