The headlights are sealed beam lamps (fig. 2-57) that illuminate the road during nighttime operation. Headlights consist of a lens, one or two elements, and a integral reflector. When current flows through the element, the element gets white hot and glows. The reflector and lens direct the light forward.

Many modern passenger vehicles use halogen headlights. A halogen headlight contains a small, inner halogen lamp surrounded by a conventional sealed housing. A halogen headlamp increases light output by 25 percent with no increase in current. The halogen

The headlight switch is an ON/ OFF switch and rheostat (variable resistor) in the dash panel (fig. 2-58) or on the steering column (fig. 2-59). The headlight switch controls current flow to the lamps of the headlight system. The rheostat is for adjusting the brightness of the instrument panel lights.

Military vehicles that are used in tactical situations are equipped with a headlight switch that is integrated with the blackout lighting switch (fig. 2-60). An important feature of this switch is that it reduces the possibility of accidentally turning on the lights in a

Figure 2-57.- A typical sealed beam headlight assembly.

Figure 2-59.- Steering column mounted headlight switch.

Figure 2-60.- Blackout light/ headlight switch.

blackout. With no lights on, the main switch can be turned to the left without operating the mechanical switch to get blackout marker lights (including blackout taillights and stoplights) and blackout driving lights. But for stoplights for daylight driving or headlights for ordinary night driving, you must first lift the mechanical switch lever and then turn the main switch to the right. The auxiliary switch gives panel lights when the main switch is in any of its ON positions. But it will give parking lights only when the main switch is in service drive (to the extreme right). When the main switch is off, the auxiliary switch should not be moved from the OFF position.