If after installing an MSD In Control, your tachometer, fuel pump relay or electronic fuel injection (in foreign vehicles) doesn't operate correctly, your application may require a Tach Adapter. This is due to the trigger signal not being strong enough to trigger both the MSD and the factories components. If you are triggering an MSD Blaster, 5, 6, SCI, or 7 Series In with its white wire or points terminal, you will need the PN 8910 Tach Adapter. It will correct the operation of most voltage-triggered tachometers or fuel injection systems that do not work directly off the tach output terminal of the MSD Ignition Unit.