Tonight ran into issue, when I turn the key to the ON position, the tach needle jumps to 500ish. I took apart the dash last week so I could repaint the plastics. Everything was reconnected correctly, I triple checked. No wires/plug were broken during the process. All of the connections look clean. When power is off, needle rests at 0.

I'm not sure what to do at this point.

 

I had a similar issue recently, my speedo was either revving with the tach or sitting at 20 depending on how it felt that day. I recently refinished my plastics aswell so I pulled everything out.

To solve it I removed everything again, checked for continuity in all wires, checked for shorts, and checked grounds. Everything was fine so I put it back together and it went back to normal. I attributed it to a bad connection behind the cluster.

You may want to just remove the plugs, clean the, and plug them back in.