Connect the loose blue pigtail wire in the provided adapter harness to any 12V+ switched ignition source. This source can be any circuit under the hood that has 12V+ when ignition switch is in the "Run" position, and NO voltage present when the ignition is in the "Off" position. This circuit will only draw about .5 amps, so the circuit does not have to be very heavy.
NOTE: EVEN IF YOUR VEHICLE'S STOCK ALTERNATOR HARNESS WILL PLUG INTO THE MECHMAN ALTERNATOR, THIS EXTENSION HARNESS MUST BE INSTALLED FOR PROPER ALTERNATOR OPERATION.
NOTE: It does not matter if your stock vehicle connector has 1, 2, 3, or all 4 wires going to the original alternator harness. The alternator will still function properly if you connect this adapter harness as instructed.