Ok...I have an original rs/ss camaro that has the tach and gauge package. I know I made a mistake by buying a painless wiring harness including the rs headlamp harness...almost everything works except for the tach and windshield wiper motor. I thought it was my tach so I bought a new one last week...well it still doesn't work. I want to wire it directly to the back of the tach...but have no idea which is the positive or negative. There are no marking indicating anything on the back of these original tachs. Anybody have an idea? I can send a pictures if needed...and if I did get it to work...I have a HEI system. I've heard there are problems with getting a correct reading. Do I have to attach a resistor in series to it? Almost complete...just need an extra boost before I throw the painless harness in the garbage and buy an original harness.