Hey guys need a little help with a buddys 89 gta tach not working, tach input into dash is good. I know that tach is bad. Bought used tach and that one is not working ethier. hooked up tach from camaro and that unit works so I know problem with tach. So I see post on repairs performed on camaro tachs but what about firebird tachs? does any body have input on repairing these units?