Electronic odometer runs fast, speedo okay, 126 - PeachParts Mercedes-Benz Forum

johnbrady · #1 10-04-2010, 07:53 PM

90 560 SEL- the odometer is now clocking about 2 miles for every 1 mile driven. The speedometer is working okay. The gears on the odometer are good. Thanks in advance for you help.

Hit Man X · #2 10-04-2010, 08:31 PM

Did you just buy this car?

How are you verifying this?

johnbrady · #3 10-04-2010, 10:26 PM

I have owned this car for 10 years. It just started doing this. I have verifed it with mileage markers on the highway. It's very obvious even when driving at city speeds.

tinypanzer · #4 10-06-2010, 12:01 PM

I think I may know what is going on... After my differential fell out and the rear axle speed sensor broke, not only did my ABS light come on, but my odometer stopped working. My speedo still works fine. That means that the two systems are separate, and use different sensors.

So, either the sensor is acting up, or the odometer circuit is acting up.

tinypanzer · #5 10-11-2010, 11:14 AM

Well, my last reply was full of it. My odometer started working again by itself, while the sensor was still busted. Closer examination revealed yet another odometer gear that is now missing a tooth. So, forget my whole theory in the last post. Look for a gear missing a tooth or two.

EDIT-

I see now that your odometer is running fast which is quite odd. Must not be a missing gear tooth.

Since the speedo and the odo use the same sensor, I now know, the problem must be in the cluster itself. If it were the sensor, the speedo would be running fast as well. I've never studied that circuit, but checking for bad solder joints and old bulging capacitors is a good start. It might just need a couple new caps. Really hard to say without having it on the bench. On the plus side, these clusters are readily available at boneyards. I just picked up a really nice one this weekend at Pick N' Pull for $25.