2021-06-28 Repair of W124 odometer

The odometer of our 1996 W124 stopped working at some point. It simply didn't count up the milage any more. Sometimes it could be started again by using the reset switch, but then even this was not possible any more.

So I had the opportunity to pull the whole speedometer from the dashboard 😉. To do this you really need those two clamps (140 589 02 33 00) from Mercedes. Otherwise you would scratch the case for sure.

Before starting to pull the case, the speedometer cable needs to be unclipped. The clip is in the footwell, attached to the fire wall, near the break pedal. This is really important so that the cable is not bent. Otherwise the speedometer needle would wobble afterwards.

After pulling the case about as much so that you can reach inside you have to unscrew the speedometer cable. Its attached in the middle of the case. Then each cable and each bulb has to be unclipped or undone. Don't worry they are marked or fit only into one position. The plugs might be quite stuck after more than 20 years. So there is some gentle force needed to open them. Especially the big round one with many contacts.

The case can be lifted upwards without undoing the steering wheel or so. Its tight, but it fits.

Now you can open the speedometer. There are some screws to be undone. The are of different kind, so keep track of where they need to go! The screws marked with a narrower red circle in the picture needs to come off after the components are separated.

Be careful when lifting the three components, they are connected by several cables.

You should be able to pull the center component with the odometer by now.

Here is the culprit: the little green gear on the shaft of the odometer is driven by a worm gear. In my case the little green gear was loose on the axle and therefore the odometer was not working any more.

I pulled the gear from the axle and carefully degreased both the gear and axle. Then I applied a Cyanoacrylate glue. To speedup the drying process I also used a primer. Then I reassembled everything making sure no screw was left behind.

To reinstall the speedometer, first attach all cables and light bulbs, make sure to put each bulb in the according hole. They are all marked. Then reattach the speedometer cable and then firmly press everything into the dashboard. Make sure that everything is working as expected (e.g. the reset knob, the lights, indicators a.s.o.)

I got inspiration and encouragement from this website. Here are some more possible faults explained.