Speedometer; ghost in the machine?

[mooncalf]

I have an 83 928 S. The speedometer works sometime, then it stops for no reason. When I first got the car last year, the reset button for the odometer seemed to fix the problem, but as time has gone on, it works less often and the reset switch seems to have no effect.
Whaddayathink? Is this a dirty connection of some sort? Is there a speedo cable to replace?

[Mat 71]

I have the same issue. Still haven't had a chance to go look...although the last few drives it has been fine for the whole drive.

Rogue - Where does it connect in the spare tire well?

m.