W124: mileometer

Hi folks,
The mileometer of my W124 300TD stops working after maybe hundred meters. The car has 470.000 km. Any idea what to look for and if I can repair this
myself?
TIA, gaise
W124 1988
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
First: How good are you tinkering? If you're pretty lousy don't go any further. If you're not affraid to dig into the speedo you can fix this yourself. I did it on my 124 and it has worked great for more than a year now. The problem is a loose plastic wheel on the drive end of the shaft which contains the number reels. Pull the instrument cluster from the dash. If you don't know how to do this create another post. Remove the speedo and look for the plastic wheel on the end of the shaft which meshes with the worm gear driven by the speedo cable. Do your best not to mark up the number reels or to remove the shaft with the reels from the mount. What I did was force the shaft enough toward the opposite end of the mount, away from the spiral gear. My purpose was to expose the portion of the shaft upon which the gear normally rested. I then used a spring-loaded center punch to mar the shaft in two places where the plastic gear is normally positioned. This is to create a sort of splined area on the shaft. I then lightly tapped the shaft back into its original position and turned the worm gear assembly by hand to see if everything worked properly. In my case it did and I simply reinstalled the speedo. Warning: If you completely remove the shaft with the reels and the corresponding cogs which force each subsequent wheel to turn once when the preceeding wheel turns 10 times, you're in for an interesting afternoon trying to reassemble the unit. Should this happen you might be further ahead to simply turn each wheel to zero and set the wheel drive cogs properly. If you don't do this exactly right the number reels will not align perfectly once it's reassembled. You can almost always tell when a speedo has been fooled with by observing if each number aligns properly in the window showing the vehicle's mileage. Whenever you look at a car with the possibility of purchasing it make sure all of these wheels are aligned perfectly and the numbers are all straight across from each other. However, it is obvious the far right reel, when looking at the speedo from the driver's seat, usually won't be aligned perfectly, but the rest should. I looked at a speedo pictured on an MB on eBay and the numbers were not aligned all the way across. One was out of position, a guarantee the speedo had been turned back. Good luck!
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Thanks for your answer Ernie. I am not lousy but really don't know how to remove the dash. I'm looking for some W124 manuals on ebay right now, might be useful....
regards, gaise
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
If yours is like my '81 240D and 300D removing the dash is probably the easiest part of the job. What you do is get a couple of very flat pieces of, stiff metal about 1/4-inch wide and maybe 4-6 inches long. Bend about 1/16-inch (or less) of the end of each piece at least 90 degrees. Push these into the gap between the plastic instrument cluster and the dash in the upper corner on each side with the small right-angle ends facing down. This will allow them to hook onto the instrument cluster. Pull the dash out. On my 240D you have to remove the ground wire and pry off the electrical multi-pin connector and disconnect the oil pressure line. Then you have to unscrew the metal "nut" holding the speedometer cable in place. With a little twisting and turning the cluster should then come out so you can unscrew the speedo unit from the back of the cluster. Good luck.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
the hooks will look like ice block hooks
my Mr. fix guy let me use his
the case, minus a few cans!
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Hello,
I had the same problem with my '89 300e--the plastic gear was spinning on the shaft. I removed the cluster and then the speedometer and took it to a clockmaker. He knurled the shaft, pushed the gear back on along with some epoxy and now it works as expected. Turned out to be a $20 "while-u-wait" kind of job.
Mike

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Good idea! Hadn't thought of taking the speedo to a watch repairman. Will log that into the frontal lobes.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.