In one position, the high beams are turned on, and, in
the other position, the dimmer changes them to low
The headlights can be aimed using a mechanical
aimer or a wall screen. Either method assures that the
headlight beams point in the direction specified by the
vehicle manufacturer. Headlights that are aimed too
high can blind oncoming vehicles. Headlights that are
aimed too low or to one side will reduce the operators
To ensure that the headlights are properly aimed,
you should have a half a tank of fuel, the correct tire
pressure, and only the spare tire and jack in the vehicle.
Some manufacturers recommend that someone sit in
the operator and passenger seats while aiming the
HEADLIGHT AIMERS are a device for pointing
the vehicle headlights in a specified position. They
may be permanently installed on a track or may be
portable. Some require a level floor, and others have
internal leveling mechanisms to allow for uneven shop
floors. To use the aimer, follow the instructions for the
specific type of equipment.
The HEADLIGHT AIMING SCREEN is a series
of measured lines marked on a shop wall or on a framed
easel for aiming the headlights of a vehicle. The screen
should be no less than 10 feet wide and 42 inches high.
When it is mounted on an easel with casters, the screen
should be no more than 12 inches from the floor. To
comply with regulations of most localities, you should
place the screen 25 feet ahead of the vehicle.
The accepted driving beam pattern for passenger
vehicles will show the high intensity portion
(hotspot) of the light rays centered on a horizontal line
that is 2 inches below the center or horizontal
reference line on the screen (fig. 2-63). This means
that there will be a 2-inch drop of the light beam for
every 25 feet of distance from the headlight.
Headlights on large trucks present a special
problem because of the effect of a heavy load. At the
same 25 feet, truck headlights should be aimed so that
none of the high intensity portion of the light will
project higher than a level of 5 inches below the center
on the headlight being tested. This is necessary to
compensate for the variations in loading.
When using a screen for aiming the headlights on a
vehicle that uses a four-headlight system, adjust the
hotspots of the No. 1 (inboard) lights so that they are
centered on the vertical lines 2 inches below the
horizontal line (fig. 2-64). The low beam of the No. 2
(outboard) lights is aimed so that the hotspot does not
extend to the left of straight ahead or extend more than
6 inches to the right of straight ahead. The top of the
hotspot of the No. 2 lights is aimed at the horizontal
line. When the No. 2 lights are properly adjusted, the
high beam will be correct.
Figure 2-63.Accepted beam pattern for aiming passenger vehicle headlights.