Hello all,

The odometer in my 86 300SDL stopped working all of a sudden. Both the odometer and trip odo are dead.

The speedometer still works perfectly.

Took the thing apart and there is a 1" "wheel" on the side of the speedo itself. It has a plastic cover on it and once you remove the cover, the 1" wheel can be pulled out. It's some kind of magnet that apparently spins.

Spun the magnet by hand and it makes the odo turn.

However, ALL the gears turn properly and the mileage accumulates when spinning this wheel.

So my thought is this: something is wrong with the board in the unit. I tested the cable and it is sending the proper signal to the cluster. And spinning the wheel causes mileage to accumulate (ie. not a gear problem)

Any ideas on what to check? Am I right in assuming the odo assembly (gears, shafts, wheels, etc.) are working and therefore it's the circuit board?

Thanks!
Neal

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'83 300SD 335,000km (207k) mi SOLD
'87 560SL 163,000km (101k mi) SOLD
'86 300SDL 356,000km (220k mi) SOLD
'92 500SEL 250,000km (155k mi) SOLD
'90 300SL 140,000km (87k mi) SOLD
'01 S430 260,000km (161k mi) SOLD
'03 SL500 167,000km (104k mi) SOLD
'07 S550 4MATIC 235,000km (146k mi) SOLD
'07 GL320 CDI 4MATIC 348,000km (215k mi)
'13 GL350 BlueTec 4MATIC 170,000km (105k mi)
'14 SL550 72,000km (43k mi)

I'm pretty sure that the gear that usually breaks is quite smaller than an inch.

I've attached a sideview of a gear that is similar in size. I believe yours is probably black in color (if any of it is still there).

It really is a small gear ...a little bigger than the eraser end of a pencil.

Attached Thumbnails

 

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It is a truism that almost any sect, cult, or religion will legislate its creed into law if it acquires the political power to do so. Robert A. Heinlein


09 Jetta TDI
1985 300D

Mine in my 300SD broke in the late 90's. I kind of like not having the "instrument of doom" stuck in my face all the time. I keep track of service with how much fuel I run through the car sort of like having a hobbs meter like on aircraft engine.

Broken odometers are common on these cars and most buyers are aware of the issues.