| It depends - which shift light are you using?
If you are using a Auto Meter, The green wire reads the electrical pulses from the ignition. For most standard ignitions it connects to the distributor primary or negative (-) side of the ignition coil.
WARNING: Do not connect to coil on MSD ignitions. Some electronic ignitions have a tach terminal on the ignition box, the green wire may connect there. Before installation read instructions. For new ignitions without distributors, contact the Auto Meter customer service department for more information.
If you are using an MSD digital shift light...
Do NOT connect to the coil (-) terminal. The supplied GMR pickup must be used
when installing the Digital Shift Light unless the rpm signal is coming from the tach output of an MSD Ignition or aftermarket ECU. Damage to the DSL will occur if connected to a high voltage trigger source.
The Shift Light installs easily with the GMR Pickup or through the tach output terminal of an MSD Ignition Control or aftermarket ECU. It will accept a trigger signal rated from 0-24 volt amplitude. Never connect the Green Wire directly to the coil negative terminal  | 
Linear Mode
