XSP311

The XS Power XSP311 is the wiring harness that connects an XSP310 Voltage Control Module to GM SI series alternators used from 1969 to 1988. It is the application-specific piece of a voltage control install, sold on its own so you can match the harness to the alternator in your vehicle.

GM SI series alternators covered a long production run across trucks, vans, muscle cars, and work vehicles, which is why they show up so often in hot rod and high-power audio builds today. The XSP311 gives that alternator the correct connection to the VCM, so the module can set charging voltage rather than leaving output to the factory regulator.

Buy it as part of a fresh voltage control install alongside an XSP310, or as a replacement if a harness has been damaged, chewed up in an engine bay, or lost during a swap. It is also the part to add when you already own an XSP310 and are moving it into a different vehicle with an SI series alternator.

Check your alternator series before ordering. SI series covers 1969 to 1988 GM applications; CS series alternators from 1986 to 1997 use the XSP312 harness instead. Matching the harness to the alternator is what keeps the install clean and the voltage control working as designed.