H4 Upgraded Headlight Harness - K Suspension H4 Wiring Harness Upgrade for any vehicle with the H4 light plug Increase your OEM lighting output by a minimum of 50% (usually more)Save your light switch from burning up like they always doTake the load off the system and wire your lights directly to the battery!Plug 'n Play designNo wiring needed Watch our video below for some guidance on how the install will go! Jeep Headlight upgrade for the YJ Wrangler and XJ Cherokee. Jeep Headlight Upgrade Jeep headlight upgrade is in order for all YJ & XJ's. Yes you can add all kinds of off-road lights on the bumper, below the windshield or even a light bar above the windshield. But in some states it is illegal to run aftermarket lights on the highways.