Tachometer is not functioning / inaccurate after installing the Ignition system

Occasionally after upgrading to electronic ignition, some tachometers experience compatibility issues. In most cases we are able to get the tachometer to function again using one of the two methods. There are two basic forms of tachometers we encounter. The first and most popular uses the coil negative signal to determine RPM. The second is wired inline with the primary ignition circuit and registers RPM off the current.