The VSS has 3 wires, center wire always 12 volts (with the key on), black wire ground, and yellow-blue wire output. Check that the power and ground are good at the sensor.

Jack up one front wheel and put the transmission in neutral (key on but engine not running). As you rotate the wheel the voltage on the output wire should vary in an on-off manner. I think it goes from ground to 12 volts though it may not rise all the way to 12 volts. If it stays at ground unplug the sensor and measure ohms from the output wire to ground to see if there is a short in the car wiring.

 

thanks guys for all your help but i finally fixed it!! I removed all of the neon tubes & mounting hardware and voila' the speedo started working!! I'm thinking that one of the mounting screws was grounding out something???? Either way, he has no neons now but he has a speedo!