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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.
What you need
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You'll need to begin by removing the instrument cluster from the car. You can read the removal guide for this process if you need help with this.
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If all of your odometer gears check out, you can then test the odometer operation to see where the problem lies.
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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.
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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.
Josh, we used a drill bit that fit snugly in the opening for the speedometer cable. A square bit works best as it matches the shape of the end of the cable.
Hello all. I have a similar problem but with the daily miles counter. He stops everytime @ 29.9 miles and doesn't go further. Is this guide useful then ?
Kr,
Bart
This would be what I would try first, yes. This is also known as the trip odometer. It is driven off the primary odometer. If the primary is slipping it will also cause the trip odometer to not work properly.
Hello Nicolas,
It's only the trip odometer that causes the problem (sorry for the bad translation - i'm living in Belgium and bought a W123 USA). So what should i do then ? The odometer works fine. So I don't like to open it up when it works fine like it does now...
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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.
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This grey gear is the main odometer gear that turns the small plastic gears along the top of the odometer numbers.
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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.
bei mir liegt irgendwo zwischen welle und hauptanteieb, das problem, beide lassen soch einzeln antreiben aber nicht zusammen
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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.
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It isn't easy to take a picture of, but the shaft has been scored in a cross-hatch pattern.
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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.
When I did this repair, I put a little superglue on the shaft at the place of the grey gear. Just a little, so that the shaft was about 0,2 mm thicker on one side. It never slipped again.
Hello,
I can’t thank you enough for this site. It saved me a lot of money and time.
Followed your procedure and it works great
Thanks Paul V
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To reassemble your device, follow these instructions in reverse order.
To reassemble your device, follow these instructions in reverse order.
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16 Comments
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
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.
…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.
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.
No, the grey aluminium gear is not affixed to the shaft. It rides on the shaft by friction. The problem that tends to happen is that the shaft that has the brass gear on the end develops a very smooth spot there due to minor slippage over 30+ years and eventually it just slips. That is why this guide describes how to rough up that part of the shaft so it can turn the gear again by friction.
So, if I add a key to the grey gear the way I did to the brass gear, it should work as a permanent repair? (If I can figure out how to reinstall everything…)
Hi- great instructions. Thanks. But I am at the last stage and cannot get the speedo cable reattached. Is there some trick.? There’s just so little clearance!
Ok answered my own question. There’s a zip tie in the engine bay which secures the Speedo cable to a bracket. Cut the zip tie and you have plenty of room.
Where can I get correct Odometer gears for 1984 380SL?
More specifically the small 12 pt gear that fits on the motor shaft and fits over the brass bushing.
Great repair instruction. Thank you!
Buenas tardes. Gracias por compartir sus conocimientos, han ayudado en muchas ocasiones. Tengo una consulta en específico: se consiguen planos para hacer impresiones en 3d de los engranajes? Porque donde vivo es virtualmente imposible conseguir repuestos. Agradezco el tiempo que se toman, gracias por ayudar siempre
