Okay for a long time I tried figuring out why my was getting a no speed signal. I was once in a while getting a signal and 99 percent of the time not getting a signal.
So what I did was attach my obd2 scanner and I put it in speed and I hit the dash and I noticed it gave a reading. So I was 100 percent certain it was the dashboard
The only way I fixed it, removing and sanding the connecter copper plates didnt work. removing the screws didnt work, but what DID work was resoldering every single solder join I could find specificicall on the speedometer unit itself you have to unscrew it from the assembly where you have it out of the cluster. That fixed my problem and I havent had a problem since. There is one screw that looks like there is solder under it I melted that a little to and it worked perfectly. If you dont melt it really nice it wont turn shiny and burn the oxides away i think. But thats what fixed it for me
I spent so much time under the car checking the speed sensor connections. Man after 20 years or whatever it was perfectly clean down there I made it so dirty by just touching it I feel bad for it lol.