I installed a tachometer yesterday and it worked fine. Today the needle goes counterclockwise. Anybody know whats causing this problem? I hooked up a ground wire, a wire going to the negative side of the coil, a wire going to the instrument lights, and a wire to my electric fuel pump switch. Any suggestions?

 

If it worked fine yesterday but is not working today I'd bet one of your connections went south. I'd start by checking those.