Features: If, after installing an MSD Ignition Control, your ta?chometer doesn?t operate correctly, your ap?plication may require a Tach Adapter. This is due to the trigger signal not being strong enough to trigger both the MSD and the factory?s components. The adapter is simple to wire in and will have your MSD and vehicle firing away in no time! If you are using the magnetic pick-up input (green and violet wires) to trigger your MSD Ignition, you will need the PN 8920 Tach Adapter. The PN 8920 will correct the operation of most voltage-triggered tachometers that do not work directly off the tach output terminal of the MSD Control. This Adapter should also be used on current-triggered tachs (hooked in series with the ignition switch).
Click Here for a wiring diagram.