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Repairing Mercedes W123 Odometer

Inleiding

Does your odometer not turn at all? Does it turn slowly (i.e. it takes longer to roll on another mile than it should)? Does it turn when cool out, but not when it's hot outside? All of these are signs that the shaft that turns the odometer has been worn smooth and is slipping.

This is by far the most common reason for odometer failure.

You will need to take out and inspect/test the odometer to confirm this is the problem before deciding to use the remainder of this guide to fix it. If you find that another problem exists, like broken teeth on one of the plastic gears, this guide will not be of use until you replace the gear and then test the odometer again to see if you also need to undertake this repair.

Wat je nodig hebt

  1. Repairing Mercedes W123 Odometer, Repairing Mercedes W123 Odometer: stap 1, afbeelding 1 van 1
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  2. Repairing Mercedes W123 Odometer: stap 2, afbeelding 1 van 1

    • Get your cluster inside, someplace safe, and on to your work bench. Protect it with something on the bench like a towel to avoid scratching the clear plastic cover.

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  3. Repairing Mercedes W123 Odometer: stap 3, afbeelding 1 van 1

    • To get access to the odometer, the speedometer assembly needs to be removed.

    • First, however, the tachometer/clock assembly needs to be removed as it overlays on top of the speedometer.

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  4. Repairing Mercedes W123 Odometer: stap 4, afbeelding 1 van 1

    • Remove the screws holding the tachometer/clock assembly to the back of the cluster. There are three shown here; a fourth is obscured behind the fixer's hand.

    • You may also need to remove the rheostat that dims the instrument lights.

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  5. Repairing Mercedes W123 Odometer: stap 5, afbeelding 1 van 1

    • You will now be able to carefully lift the tachometer/clock assembly out of the cluster. Set it aside someplace safe. Do not set it face down, on the needles.

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  6. Repairing Mercedes W123 Odometer: stap 6, afbeelding 1 van 1

    • You may need to remove the rheostat that dims the instrument lights first, before removing these last two screws.

    • Next, unscrew the two remaining screws holding the speedometer assembly in place.

    • Note that it shares two screws with the tachometer assembly, on the left hand side, so those are already out.

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  8. Repairing Mercedes W123 Odometer: stap 7, afbeelding 1 van 2 Repairing Mercedes W123 Odometer: stap 7, afbeelding 2 van 2

    • You can now lift the speedometer assembly out, carefully. Note that there are wires that cross behind the gauge face; you will need to clear these wires to remove the gauge.

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  9. Repairing Mercedes W123 Odometer: stap 8, afbeelding 1 van 1

    • Now, remove the single screw that holds the black plug on the back of the speedometer assembly. With the screw removed the plug pulls out of a slot.

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  10. Repairing Mercedes W123 Odometer: stap 9, afbeelding 1 van 2 Repairing Mercedes W123 Odometer: stap 9, afbeelding 2 van 2

    • Now you can remove the two flat head screws that hold the metal back on the speedometer assembly.

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  11. Repairing Mercedes W123 Odometer: stap 10, afbeelding 1 van 3 Repairing Mercedes W123 Odometer: stap 10, afbeelding 2 van 3 Repairing Mercedes W123 Odometer: stap 10, afbeelding 3 van 3

    • Removing the metal cover will expose the odometer. Inspect the various plastic gears for broken parts. If you find any, they will need to be fixed before continuing.

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  12. Repairing Mercedes W123 Odometer: stap 11, afbeelding 1 van 1

    • If all of your odometer gears check out, you can then test the odometer operation to see where the problem lies.

    • To do this you should place a power drill, with an appropriately sized square drill bit, in to the speedometer cable opening and run the drill. Observe the speedometer and odometer function while you do this.

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    • View this video to see the test in action. Note this video was recorded after this odometer was fixed via the steps in this guide.

    • If all of the gears on your odometer turn, and the speedometer also moves, but the numbers on your odometer do not turn this is the guide for you! Continue reading.

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  14. Repairing Mercedes W123 Odometer: stap 13, afbeelding 1 van 3 Repairing Mercedes W123 Odometer: stap 13, afbeelding 2 van 3 Repairing Mercedes W123 Odometer: stap 13, afbeelding 3 van 3

    • This brass gear is the item we are interested in. It is attached to a shaft that is responsible for turning the main odometer gear.

    • This grey gear is the main odometer gear that turns the small plastic gears along the top of the odometer numbers.

    • This is the other end of the shaft the brass gear is attached to. It is held in place by a tight fitting brass ring.

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  15. Repairing Mercedes W123 Odometer: stap 14, afbeelding 1 van 1

    • Now support the speedometer gauge face and the rest of the assembly on something soft that will protect it. Some foam was used in this case.

    • Then, using a hammer and small punch, tap out the shaft shown in the last step from the side with the small brass ring.

    • Press your finger against the gear end to keep the shaft from falling out. This shaft also acts to support the numbers. Without it they "droop" down and can also become out of alignment.

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  16. Repairing Mercedes W123 Odometer: stap 15, afbeelding 1 van 1

    • As soon as the metal shaft with the brass gear becomes loose, chase it out with an appropriately sized drill bit. Go slowly to make sure you don't leave too much space between the shaft and the bit or else one of the numbers might fall out of alignment.

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  17. Repairing Mercedes W123 Odometer: stap 16, afbeelding 1 van 1

    • The shaft should now be fully accessible.

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  18. Repairing Mercedes W123 Odometer: stap 17, afbeelding 1 van 1

    • Inspect the shaft. As you can see here, the area just inside of the brass gear is very shiny compared to the rest of the shaft. It has been worn smooth by years of friction. This is what slips underneath the grey gear, leading to the odometer not turning.

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  19. Repairing Mercedes W123 Odometer: stap 18, afbeelding 1 van 2 Repairing Mercedes W123 Odometer: stap 18, afbeelding 2 van 2

    • You will now want to score the shaft using a utility knife, or other sharp object. The tip of a sharp screw driver can work. Or you can rough it up with thick sandpaper. In any case, the idea is to create a surface that is rough enough to restore friction between the shaft and the grey gear.

    • It isn't easy to take a picture of, but the shaft has been scored in a cross-hatch pattern.

    • You can now re-insert the shaft, chasing the drill bit back out, ensuring that the numbers remain in sync. Once the shaft is all the way back in, you can then use a small punch and a hammer to tap the brass retaining ring back on the end of the shaft. If needed, support the brass gear with a small piece of hard wood.

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Conclusie

To reassemble your device, follow these instructions in reverse order.

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Nicolas Siemsen

Lid sinds: 12/06/13

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18Gids Commentaar

Hi,

My speedometer needle and odometer don't work when I turn them with a drill bit. What can be the issue? Any guides for fixing?

Thanks

Vito - Antwoord

Hello Vito, as the guide says, what you are looking for is to see if the gears spin on the back of the odometer when using the drill. If the gears spin, but the odometer does not turn, the reason is the shaft being worn as noted. Use this guide to fix it.

If however the gears are not all turning on the back of the odometer it is likely that one of the gears is stripped or broken. You will need to find which gear is broken and replace it. There are sites online that sell replacement plastic gears. You'll need to do some research to find the right one(s). I haven't had to do that before.

Nicolas Siemsen -

Curious, my odometer turned to 161979 but instead of rolling to 161980 it goes back to 161970 and repeats. The trip odometer works fine...any thoughts? I am hopeful it simply starts working again. Thank you!

David - Antwoord

…it’s only my TRIP odometer that stopped working…. I’d bet it’s in the mechanism for resetting it—that is, pushing the button IN to reset the TRIP odometer to 00000….. now jammed at 190.1 or so …. and pushing doesn’t do anything. …

MAIN odometer & speedometer DOEs work as usual. ‘haven’t opened ‘er up and eyeballed it yet. THANKS for the insight here.

…by the way…just in case you’re reading this and had experience with the FUEL gauge also….I specifically can tell you…that stopped working once when I had instrument panel out (for other purposes—as if I brushed against something??)

…it doesn’t work by: being “over” to the right…such that “full” down to about 1/3rd acts normally….but it stops at 1/3rd …

in other words, it could read 1/3rd and be empty. ….

setting trip odometer, thus, becomes quite handy, as I always do…until a few days ago when that stopped working. Peace. Out. 240D 1983 380K 4 speed manual…a beauty mechanically.

83 240D and 300D - Antwoord

What about the aluminium gear beside the odo numbers? Shouldn’t that be fixed to the shaft as well? I have secured the brass gear to the shaft, and the odo is still not turning while the speedo works.

totallyplanecrazy - Antwoord

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