Trip Odometer Not Working

[Robert Scheck]

The trip odometer in my 1994 EA11R has stopped working. The odometer seems to be working fine. I have removed the instrument cluster from the car and further removed the speedometer from the cluster. Before removing the cluster cover I could hear something rattling around inside. When the cover was removed two small black plastic gears dropped out. I can't determine if they were part of the odometer mechanism. For the matter I can't tell where in the cluster they were attached to. Has anyone disassembled the odometer and trip odometer? Is there a detailed diagram of the unit? Do you not advise attempting to take a speedo apart? Should I not worry about the non functional trip odometer? Of all the things I could worry about this is a small one.

Thank you very much for your help.

Rob

[Ian Linden]

Hi Robert,

Those gears are almost certainly connected with the trip odo defect. Have you tried examining it in conjunction with operating the trip reset control - it may provide a clue? Afaik, there is no published info on the detail of that system.

If you want to take it further, it is probable that the design is one common to many vehicles. You could either find a specialist instrument technician, or ask advice from (say) ChatGPT.

[Robert Scheck]

Thanks Ian.

After I submitted my question I found another part that had fallen out of the gauge cluster. At first I wasn't sure if it was even part of the cluster. It is a small pin about 4 1/2 cm long. Both small gears fit perfectly on it. I spent a lot of time using a loupe studying the speedometer mechanism before I had a break through. You are right. The gears and the pin are part of the trip odometer reset function. One of the gears is part of the connection between the main odometer and the trip odometer. When the reset button is depressed the pin and gear assembly is moved away from the tumblers allowing them to turn freely and for the reset to occur. A simple but effective design. I am hundred percent sure where the pin and one of the gears is positioned. The placement of the second gear is pure guess work. I have reassembled the speedo but have not had time to reinstall the cluster. I also will be away for a few weeks. When everything is put back together I will test it and post if I was successful. Fingers crossed. I think I learn more about trip odometer design than I ever wanted to.

Thanks again.