Many of the '89 to '06 Cummins-powered Dodge Rams were sold with a Nippondenso gear reduction starter ... wire within the vehicle harness. The solenoid is essentially a high-current relay ...

There was a time when a hot rodder copied a basic wiring diagram out of a motor's manual ... one yellow wire was for the wiper or the starter solenoid. Kits and components aimed at such rodders ...