With key on, the connection for the temp sensor shows 10.5 volts. (This is a 2 prong sensor). So I have no idea now why the dash gauge doesn't move, I ran this until hot enough to kick my fans on (180 degrees) and the gauge still shows below the C.
When you ground the lead for the temp sensor, the gage should hit hot fast. Have someone help with this, or run an extra length of wire so you can see the gage when you ground it, with the switch on. Exhibit care so as NOT to burn up the gage in the dash panel.
You have the wrong sensor. The 2-pronged is for the ECM. You should have a single connecter sensor near the thermostat housing - NOT on the intake manifold. If you are in the right location, then somebody has installed the wrong sensor.
Also, there is a good chance it's been pulled loose or left disconnected after previous maintenance
They must be either foreign, or really old, because I've worked on domestic stuff all the way back to the 40's. I'd like to see an example if you can find one.
You are correct, I found the other connector (single, flat blade) and grounded it, and gauge went straight to the top. So, I have ordered a new sender for that. Which sucks monkey balls cause that 2 prong sender was like $45.
Maybe the "reverse rotation corrector" fittings I saw were made to work with these weird racing speedometers. Lord only knows why they would go out of their way to buy them, but to each their own.