The 5 inch Sunpro Tach in my Bel Air quit working for some reason. Checked all of the connections, made sure I had a good ground, and made sure there was a signal from the distributor with my test light. My multimeter was dead so I couldn't check the voltage. After all of this, it still won't do anything. I can't even adjust the shift light, or check where the shift light is set. So then I took the old Suntune tach that was originally in my Bel Air (worked when I put the Sunpro in) and decided to put it in my 1981 Chevy K20. I hooked everything up the right way, and when I start the truck the needle will just flicker, but it stays at 0 when the truck is running. Then when I shut the truck off, the needle will flicker again. I checked all of my connections and the ground with my test light and they were all good. So are both tachs really burned out??