Speedometer incorrect

[George300SL91]

I have a 1991 300SL that I had to replace the odometer in I got the odometer from a 500SL when I am doing 80mph on the odometer I am doing 60mph on radar is there any way to correct the speedometer?

[lino]

From what I have been learning so far, a speedometer should be replaced with one from another car that has the same engine. Also, older cars have the speedometer connected by a cable and newer cars have electronic versions. Another difference would be an anlolog odometer as opposed to a digital one obviously. I think 1993 was the last year for the analog.

For example in my case, I have a 1989 300ce with the M103 engine so a 1990 300ce with the M104 engine would have a speedometer that is not compatible with my car. That's probably what happeded to you in the case of the 500SL.

You probably can use one from the following cars:

1990-1993 300SL
1992-1993 300SE

Don't quote me though. I am only offering you what I "think" might work.
Good Luck. Hope this helps.

[George300SL91]

Ok but is there any way to adjust the speedometer I have now?

[lino]

Originally Posted by George300SL91

Ok but is there any way to adjust the speedometer I have now?

Not that I know of. You may want to call these people and see if they can help you:

http://www.paspeedo.com/mercedes.htm

http://www.nhspeedometer.com/

[George300SL91]

I will check them out

[nellotare]

Here in Wilmington there is a shop that calibrates speedometers (as well as repairing old or installing new "heads" as they call them). They are accepted/recommended by the Police Dept. Perhaps your community has a shop like that?

My tires on the Jag were oversized so if speedo said 70, I was really doing around 80. That shop was available if I wanted my speedo accurate with the size tires I was running, and the police were all for my speedo being accurate. I did not opt for that option and don't know what they did to recalibrate, but the shop only worked on speedometers and no other instruments.

[stevebfl]

To calibrate an electric speedo one places a prescribed frequency into it with a signal generator. The frequency is noted on the back of the speedo K or W equals xxxx. This frequency should produce 60mph.

Due to the different drive ratios of the differentials the numbers will be different from speedo to speedo.

There are folks who manufacture speed signal modifiers. The idea would be to take your speed input frequency and reduce it by 25%.