1985 500SEL
Speedometer work but Odometer does not , anyone how to fix this?

 

sounds like you have the same instrument cluster that I do in my 123's
My experience with one of them is that the trip odometer has a spring that gets lazy or gummed up and that unless I let it snap back rather sharply when I reset it, it will go to 9 tenths of a mile and stay there. Since the speedo cable drives the trip odometer and the trip odometer drives the odometer, that's where to start. Otherwise you'll be pulling the cluster
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