Alternator
Most LS alternators need a switched 12V excitation (sense) wire to start charging. This is not a plain battery wire — it must include the correct resistor or a purpose-built harness.
Excitation Wire
Options:
- Wire into a Holley ECU input that can provide the correct signal, or
- Tap a switched source at the driver's-side fuse box with the proper resistor inline.
A convenient option is the Sloppy Mechanics Holley plug-and-play flex-fuel + alternator combo harness.
For real-world photos of alternator wiring and resistor setups, check the Swapped GCs and Genesis Coupe LS Swaps groups.