Abstract: A motor vehicle has a daytime running light system for providing automatic illumination of a pair of headlamps at reduced intensity. The reduced intensity operation is accomplished by way of a switch mode power converter which operates to provide a daytime running light voltage that is less than the vehicle system voltage normally supplied to the headlamps. The switch mode power converter makes extremely efficient use of the vehicle electrical power by minimizing power dissipation in attaining a lower daytime running light voltage. Furthermore, the daytime running light system is amenable to simple calibration modification to implement varying daytime running light voltage levels in accordance with vehicle system and/or various international requirements.