This is a Parts Place Tach. Worked well for about 3 years. Even when first installed, every time I started the car (when cold and took a bit to start when car sat for a while), the tach would go all the way and sometimes back and forth until the car started... then eventually it would work sometimes if I was lucky... now doesn't work at all. Looking for some help to test the tach outside the car now that it is removed. If I remember, the "S" came from the negative on the coil and the "+" is 12v from ignition on? Am I overthinking this and shouldn't it be as easy as (under the hood) running a 12v wire from the battery to the "+" and then direct to the negative of the coil for the other conection? Thanks