My odometer finally stopped working! Also more questions - PeachParts Mercedes-Benz Forum

86560SEL · #1 05-05-2009, 08:50 PM

Did a search and found SOME info, but not nothing really that helpful and I have a couple of additional questions anyway.

Well, out of all of the Mercedes I have had, I finally have one that the odometer stopped working on... on my '88 W126. It had to of stopped working the last time I drove it, which was this past Sunday. My fuel gauge is not that accurate, so I use my trip odometer as a "guide". I guess that was a no-no, because it probably helped it stop working sooner than it would have where I was resetting it. ? Anyway, no the trip odometer AND mileage odometer have stopped. Its now on 156,539 miles and stuck as of today. I want to get this fixed asap, but wondering whats the best way to do it and what will a indy shop normally charge for this and what parts do I need and where can I buy?

Also, ALL of my warning lights EXCEPT the battery, anti-lock and check engine lights are fairly dim. Battery, anti-lock and check engine lights are bright. Does this sound like those other bulbs may need replaced, or is that some other issue? I thought while the cluster was out, it would be a good time to replace these warning bulbs.

My SRS indicator light dont even illuminate.... either a bad bulb, or someone disconnected the system?

Also, while my dash illumination bulbs are fairly bright, I would not mind upgrading to those LED bulbs everyone has been boasting about while the shop has the unit out.

Thanks in advance.

tinypanzer · #2 05-05-2009, 10:42 PM

I just dealt with this issue recently, and it's not too bad a job.

First, you will need to order the 12 tooth gear from odometergears.com, or at least that was the gear used in my '90 300SE. I think yours should be the same.

Then, you have to pull the instrument cluster out, which is really no big deal at all. You can do a search here and see how to make the tools and how to use them. Easy.

Then you just have to open up the cluster enough to get to the broken gear. It is the tiny gear that sits on the end of the motor shaft that drives the odo.

You will notice that the plastic gear that was on there has split, leaving the metal insert that was once part of the gear on the shaft. You do not have to remove this insert. The new gear is designed to go over it. Here's the tricky bit - pressing the new gear on there. It's a tight fit, and mine never went all the way on, but it went on far enough to hold well and work properly. At some point I just decided that I was more likely to break it if I applied more force to get it to seat 100%. It has worked fine. Forces are so tiny that it's plenty "on there" to hold.

Once you get it seated, I would apply a dab of vaseline or similar heavy grease. The new gear has the tendency to be a bit noisy under certain conditions, particularly when it's very cold. Odometergears.com says this is normal, I say they could have done a better job of making that not happen.

Then the light bulbs - some have little plastic bases that twist-lock into cutouts on the circuit board of the cluster. Others are hard wired to the harness inside the dash. The twisties are easy to replace, the other ones require a splice and solder or a crimp.

Here's the cool thing - you can get all the bulbs you need from a junkyard cluster because only a few of the bulbs ever come on long enough to wear out and get dim. Those are the frontlighting bulbs, the low gas bulb, the brights bulb, and maybe one or two others. The rest of them only come on for a few seconds when you start your car and never accumulate any wear.

You can tell if the bulb is dim or not by if it has a silvery coating inside the glass. That coating is actually metal that has evaporated off of the filament and deposited itself on the glass. Very easy to spot.

If you can't find any, I have several good used cluster bulbs of both the twist-in and hard wired type.

Holler at me if you have any questions about it......

Cal Learner · #3 05-06-2009, 08:26 AM

Am I wrong about this, or isn't it by design that some of the idiot lights are dim and some are bright? Can't remember offhand where I saw that, but it seems like it was in the FSM. That doesn't mean that the OP's bulbs aren't dimmer than they should be and would benefit from being replaced when the cluster is out.

tinypanzer · #4 05-06-2009, 06:23 PM

That wouldn't surprise me if some were dimmer by design, but the bulbs appear to be all the same, so if that is the case than the different brightnesses are probably accomplished with external resistors..... I assume....

86560SEL · #5 05-08-2009, 12:08 AM

Thanks a bundle for the replies and information! At the concern of me breaking something, I will probably end up letting my "indy" Mercedes shop do this work on the odometer. I dont think he would charge to much to do it.

I am not sure about the warning lights, why some are brighter than others, but I know that my 1984 190D and 1985 380SE were identical.... some warning lights were quite dim and dimmer than others. It may be normal... maybe someone that bought one of these brand new or have one thats still with ultra low mile and new mint condition may have more info on this?

Thanks again!

Hit Man X · #6 05-08-2009, 12:48 AM

Sounds like a fairly simple fix.