An automotive vehicle exterior illumination circuit includes a main headlamp circuit, including a headlamp switch, for operating the headlamps at full intensity and a DRL control incorporating voltage-dropping resistance in a daytime running headlamp circuit for achieving reduced intensity daytime running illumination. The resistance is provided by a plurality of resistance wires mutually connected in parallel in a wiring harness carrying electric current to the headlamp filaments. The headlamp switch is provided not only with the usual set of normally open contacts that close when the headlamp switch is turned on to provide full nominal supply voltage to the similarly rated headlamps, but also a set of normally closed contacts that allows DRL operation when the headlamp switch is off but disallows DRL operation when the headlamp switch is on. A fog lamp system is associated with the main headlamp circuit such that fog lamp operation is allowed only when the headlamps are turned on by the headlamp switch and low beams are selected by the dimmer switch. Fog lamp operation is otherwise disallowed, including disallowance during daytime running illumination.