[Formerly Steve Wilkinson]

I had endless problems getting the speedo to work in my '83 SC after I diassembled and restored it. This probably isn't your problem at all, but what finally turned out to be mine was that I'd replaced the sensor on the transmission case backward. I knew perfectly well that this was possible, so I carefully replaced the sensor with the "potted" side--which certainly seemed to me to be the "working" side--facing inward. That was the wrong way: the metal side should be against the transmission case.

Anyway, I also kept testing the sensors I was buying and replacing--since I assumed the sensor(s) was bad--with a multimeter, since somebody told me there was simply a coil in there and that if the sensor was good, the circuit should be complete. Well, I kept getting indications of no continuity, so I assumed the tiny coil was burned out or something. What I finally learned was that you have to put a magnet against the outside of the sensor to activate the reed switch, which then makes a complete circuit. Do that and if you get an indication of continuity, the sensor is good.

The two wires from the sensor to the connector inside the center tunnel of the car can go either way; there's no "proper" order of connection.

Test the wires from the connector in the tunnel to where they connect to the speedo and make sure you've got continuity there.

Test the power wire to the speedo to make sure you're getting 12 volts there.

We can go into this deeper, if you wish, but try those things first and let me know if this solves it. And be sure to make the connections on the back of the speedo correctly. You'll blow a diode if you don't.

Stephan