[1983380SL]

I have an 83 380sl that ive been trying to figure out why I can’t get the odometer to read. This car was purchased brand new by my sisters late father in law. When he passed away approx 30+ years ago, my brother in law gained ownership. Unfortunately, my brother in law passed away a few years ago and my sister didn’t want to see it sit... So I gave it a home, the car was well maintained it’s entire life, only going to Mercedes dealerships for all its service, including quite some extensive maintenance work. It now has 88k miles on it and all of a sudden the odometer stopped working on a ride to get coffee last weekend. After hours up hours of research, it led me to pulling the cluster out and taking a look. I immediately seen broken gears, so went ahead and ordered a set. Did the repair smoothly as per a thread on here actually, but did not resolve the issue. Everything else on the cluster works, aside from the clock (which I know from reading, that’s also prone to need repair). My main concern is the odometer though. I have a multimeter to troubleshoot, but don’t know where to begin. I’d love to be able to verify it’s getting proper signal to the stepper motor or whatever magnetic system it uses to drive the odometer gears. I can spin the shaft and see that the gears are working correctly and odometer moves. Once installed back in the car, nothing. Looking to see what my options are. Any advice is greatly appreciated.

 

[1983380SL]

 

[rick]

Be very sure you were sent the correct gears with the correct tooth counts. If not correct, they will bind. Be sure the gears turn smoothly. You can pull the cluster and visually check motion on the gears, maybe after you have removed one to eliminate binding issues in order to be sure the stepper motor is working.

 

[1983380SL]

The last paragraph states that I’ve already verified that they work correctly and operate the odometer when I manual spin by hand. The cluster has been in and out 20 times checking to see if there is anything I possibly missed.

 

[1983380SL]

Was hoping I’d get some suggestions here 😞

 

[1983380SL]

😞

 

[AlterSchinken]

It looks like there are a couple small motors that drive the gearset based on the speed signal that also drives the speedometer. Perhaps resoldering the joints on the board may correct an age related issue. I have done this to both my cruise control and climate control boxes and restored function to both.

 

[1983380SL]

I’m going to remove it again today to check something. I seen a small rectangular fuse type piece soldered in a board on back... I noticed a hole in the center, after some finding some new pictures I think that it might be blown. I just want to figure it out, I don’t think the motor is working. I wish I knew what made it work so I could bench test. Also don’t know if it’s getting the proper signal even though the speedometer works.

 

[AlterSchinken]

The only way I can think of testing it is to find out what type of signal is sent from the sensor in the tail of the transmission, then duplicate it with a signal generator while applying power & ground to the appropriate terminals. I can't find the sensor on any of the diagrams I have, and I don't know if the signal goes to the speedometer first and then to the cruise control amplifier or the other way around. In any case if the speedo reads accurate the signal must be good. There is only one speed sensor. I suppose with a scope one could read the signal while running on jacks.

 

[Aussiemerc]

It will be very interesting to learn the resolution of your problem. Good luck.

 

[plinker17722]

That would be the first thing i would replace ,, the item with the blow hole in the centre..