Nice odometer fix, and my speedo doesn't work now!? W123
 

After some digging I determined that my malfunctioning ODO was due to the "trip" button spring thingys being worn out. I slipped some hard plastic (cut from a blank CD spindle cover) over these little "spring" strips to restore firmness. Worked like a charm!

Now my speedometer doesn't work though. It looked like there was a small metal pin inside the rear "bowl" of the speedo needle that set inside a plastic controlling grommet. Should I add a bit of sticky inside of this little plastic circle to help grab the rear speedo needle? (Hard to put all these pieces into words... sorry if it's murky).

Anyway, pics of my ODO fix!

Donor of plastic

Speedo expert please?

I have a unit out, it appears the cable drives the regular odo and gears drive the trip odo. That tells me, well, I don't know what it tells me! Sounds just backwards, but this is a Mercedes.
Good luck.

Is it possible to incorrectly reverse the plug that connects to the little black box on the back of the speedo? There's a grove on one side of the female plug, but no corresponding nub on anywhere on the male prongs. What gives?

the little black box is the speed sensor for the cruise control. only goes on one way.

are you saying the needle does not move when driving?

do the numbers move when driving for the miles drive?

the trip numbers, do they move? the 10ths should be a good indicator.

there is a magnet inside of the cup driven by the spedo cable. I don`t see the plastic controlling grommet you mention. the pin inside the cup is the end of the shaft the spring fastens to and the needle is pushed onto that.

do the numbers and needle not move?

there are two white plastic shafts that drive each other, and the end of one drives the brass gear that drives the shaft that turns the milage gears.

behind the brass gear is a grey gear which turns a small white gear which turns the dark brown gear that drives the trip gears.

could the brass gear be slipping on the shaft which is common from all the threads I have read. Diesel Giant shows a fix.



Charlie

ODO is working great.

Speedo still not working. Could the magnet just not have full contact?

Did you have the needle off and the face removed? maybe the needle isn`t seated on the shaft.

Looking at the one I have disassembled, the magnet is on the shaft that the cable spins. the magnet fits into a cup, which is aluminium. the shaft the spedo needle attaches to, protrudes into the cup maybe an 1/8 in. there is a small hole in the cup about 1/2 way between center and the edge of the cup.

the magnet spins inside the aluminium cup which sits in the steel frame of the spedo housing. now how this all works, I haven`t worked out yet in my little brain.:rolleyes:

If you are having problems with yours, pick up a few at the junk yards. all you have to do is use the spedo number part, swap a few gears for your diff ratio. then you are good to go.

count the teeth on the brass gear, the teeth on the white shaft. they do differ between years or differential gear ratios.

Charlie

Well...
 

After taking out my cluster for the ump-teenth time, I believe I determined that I had the cable that plugs into the black box on the back of the speedo in backwards! Flipped it around, works like a charm now.... The needle shakes like a scared chihuahua below 30MPH but I hoping that issue "shakes" itself out.