Tach

I have a 76 Nova with a in dash Autometer tach . I has 4 wires going to it and I don't think I have them right. They are black ,red , white and green . Could someone please help me out. The tach used to work but now it doesn't . I did some rewiring under the dash. Everything else works great . Where do the wire's go?

Heres a link to a PDF doc,,showing the autometer wiring and installation.
http://www.egauges.com/pdf/AutoMeter/468h.pdf#search='Autometer%20tach%20gm%20wiring%20code'

Black is ground

Red is 12v key on

Green goes to coil negative

White is for your light

Thank you for your help I really appreciate it!!!!:3dSMILE: