GlowShift's HEI Tachometer Signal Filter is specifically designed for vehicles with High Energy Ignition Systems, and converts the high voltage signal to a more manageable voltage, that allows the tachometer to easily read.
Note: Note: Any vehicle with a High Energy Ignition System (HEI) will require this HEI Tachometer Signal Filter. Many General Motors vehicles within the range of 1975-1990 come equipped with this ignition style. If your vehicle falls between these years, verify this is the type of ignition system in your vehicle. If so, this HEI Tachometer Signal Filter will be required to gain RPM readings.
Tachometer Signal Filter will only work with GlowShift Gauges and not guaranteed to work with other applications.