LIGHTING SYSTEM

The lighting system on automotive, construction, and weight-handling equipment includes the lamps and bulbs, clearance lights, side marker lights, reflectors, taillights and brake lights, auxiliary lights, and fuses. Standards for lights on vehicles are outlined in the

Federal Motor Carrier Safety Regulations Pocketbook.

The manufacturer provides equipment with an electrical system that supports the lighting circuits. Part of your prestart responsibility is to ensure the lights on your equipment work and are clean of dust and dirt. A good rule of thumb to remember is, if a light is on a vehicle, the light must work and be safe.

Lamps and Bulbs

Trucks and buses are lit up like Christmas trees when operating at night. In addition to the headlights and taillights, which are the minimum running lights required bylaw for all vehicles operating at night, trucks and buses must also have clearance and side marker lights. These lights outline the length, height, and width of the vehicle.

Each group of lights in a branch circuit of the lighting system is protected by a fuse or circuit breaker and is provided with a switch. Each light in the group is provided with one or more light bulbs that are rated for the particular circuit.

Light bulbs used in Navy equipment are made to operate on a low-voltage current of 12 or 24 volts, depending upon the voltage of the battery system used. Bulbs are rated as to size by the candlepower of light they produce. They range from small one-half candlepower to large 50-candlepower headlight bulbs. The greater the candlepower of the bulb, the more current it requires when lighted. Bulbs are identified by a number on the base.

Operators are responsible for replacing burned-out ^{bulbs on equipment.} Manufacturers have designed bulbs with such a wide variety of designs (fig. 4-4) that it is impossible to list all the bulbs here. A bulb design commonly used has either single or double contacts with nibs to fit bayonet sockets, as shown in figure 4-5. Because of some unique designs, certain bulbs have to be handled with care; for example, quartz bulbs should not be touched by the oil in your skin, because the oil causes the bulb to fail instantly. Because of the unique characteristics of the various bulbs, you should check the operator's manual before replacing any bulbs.

The sealed beam light is actually a large bulb (fig. 4-6). The bulb consists of a lens, filaments, and a glass reflects. Sealed bulbs also have various designs; some have filaments designed for high beam, some with one filament designed for low beam, and bulbs with two filaments designed for high and low beam.

Clearance Lights

Clearance lights detail the maximum width of the vehicle, not necessarily its height as the word clearance implies. These lights highlight the protruding unlighted front and rear corners of the vehicle that are subject to

Figure 4-4.-Bulbs.

Figure 4-5.-Single- and double-contact bulbs.

collision with other vehicles or persons, not the top of the vehicle. Clearance lights should be mounted at a height best suited to allow them to be readily seen from a minimum distance of 500 feet from the vehicle. The clearance light on the front of a vehicle should be amber in color, and those facing the rear red. Some state regulations require that larger vehicles have identification

Figure 4-6.-Typical sealed beam headlight assembly.

lights that outlines the height of the vehicle. Some vehicles have a separate switch for the clearance lights. When you are operating a vehicle at night with clearance lights, do not forget to turn them on.

Side Marker Lights

Side marker lights are similar to clearance lights; however; they indicate the full-overall length of the vehicle as viewed from the side. They must also be visible from a minimum distance of 500 feet from the vehicle. Side marker lights, mounted near the front of the vehicle, are also amber and those near the rear are red.

Reflectors

Reflectors (except for those used in the lights) are used as an additional safety precaution in case lights burn out or are broken. When mounting reflectors, ensure they are between 24 to 42 inches above the ground.

Taillights and Brake Lights

All taillights must show red and be visible from at least 500 feet from the rear of the vehicle. The taillight lens should be replaced if it is not red or contains a dot of another color or if it is cracked, broken, or does not fit tightly. A brake light is usually combined with the taillight by using a double-contact, double-filament bulb; however, it maybe a separate light. Stop lights must light up immediately when the brake pedal is depressed; that is, at the beginning of the downward action of the brake pedal. Brake lights are a safety-required item and they must be operational at all times. Burnt-out or weak lights should be documented and repaired before operating your vehicle or piece of equipment.

Auxiliary Lights

Lights that can be turned on or off for the convenience or safety of the driver or passengers are called auxiliary lights. These lights are wired to be turned on and off independently, and not with the headlights. When performing your prestart operation, you should ensure all auxiliary lights work.

SPOTLIGHTS.- Spotlights are often mounted on construction equipment and weight-handling equipment. When conducting prestart operations, always make sure the spot-lights work because you never know when you will encounter conditions or situations requiring their use.

BACKUP LIGHTS.- Backup lights are accessories for many vehicles. They may be mounted singly or as a pair, one on each side. Backup lights lenses must be colorless and must turnoff automatically when the vehicle is moving forward. Backup lights may also be connected to a audible signal. A backup light must be aimed to strike the road at a distance that does not exceed 25 feet from the rear of the vehicle.

PARKING LIGHTS.- Parking lights have amber or white lenses and are located on the front of the vehicle. They turn on and off with the same switch as the taillights.