NOTE: This unit is NOT FOR USE ON STANDARD 12V AGM BATTERIES. This module will increase the charging voltage by appx. 1.0 Volt and will swell and damage AGM batteries. Please check with your Lithium battery manufacturer to verify the proper charging voltage before installing this module! This voltage boost harness fits alternators with a GM 4 pin plug and is similar to our "plug and play" H104-L harness. The P101-L is the simplified version of the H104-L which makes it great for secondary alternator setups for a cleaner look or engine swap applications. The yellow wire gets connected to an ignition switched 12V+ source to turn the alternator on and off with ignition and the blue wire with ring terminal gets connected to the alternators threaded output stud. This harness can be used with engine swap applications where the stock alternator harness is not available, and you just need a way to turn the alternator on and off through a 12v switched connection. This harness may also be used WITHOUT THE BLUE WIRE CONNECTED as previously stated if you are currently running a regular battery but plan to upgrade later to a Lithium battery later in your build.