Lesson 4/Learning Event 2
Newer headlights use a two-filament lamp having its position fixed with respect to its mounting
socket at the rear of the reflector so that the filaments remain fixed at the proper focus. It is
necessary only to direct the light to improve the lighting of the roadway.
The most common headlamp configuration in modern automotive use is the sealed beam.
The sealed-beam headlamp unit not only provides far better and more powerful illumination than
previous lamps, but it maintains its initial brilliancy with only a slight loss throughout its life. This
is because the lens is permanently sealed to the reflector, barring moisture (which corrodes the
reflector) and preventing the entrance of dust and dirt.
When a filament burns out, the whole unit must be replaced. However, it has a greater filament life
than other types of lamps and requires no maintenance to keep it in good condition.
The sealed-beam headlamp unit is made in two types: one with a silver-plated metal reflector and
the other with an aluminumsurfaced glass reflector. The metal type contains a conventional
double-filament lamp that is sealed in the unit mechanically, whereas the glass type is its own lamp
because the lens and reflector are fused together, forming a gastight unit with the filaments sealed
into the reflector.
Two filaments are provided in the sealed-beam headlight lamp unit: one provides an upper beam
for country driving and the other gives a downward beam for passing or city driving. With the
upper beam in use, current sealed-beam lamp units provide 50 percent more light than previous 32-
candlepower lamps, and they also distribute the light more effectively. The upper beam filament
requires 40 to 45 watts, and the depressed beam filament requires 30 to 35 watts, which is more
current than that required by the 32-candlepower lamps. Directing the headlight to the roadway is
the only adjustment required on sealed-beam headlamps.
The sealed-beam headlamp is mounted with long self-locking screws and springs. The screws serve
to aim the headlamps, depending on their position.