![]() ![]() The device is not scanned for additional magic strings for the same filesystem. The wipefs command lists only the first offset where a magic string has been detected. Note that some filesystems or some partition tables store more magic strings on the devices. Wipefs calls BLKRRPART ioctl when erase partition table to inform kernel about the change. When used without options -a or -o, it lists all visible filesystems and the offsets of their basic signatures. Wipefs does not erase the filesystem itself nor any other data from the device. A vacuum switch may be added to the headlamp switch or in the circuit when vacuum doors are used over the headlamps.Wipefs can erase filesystem, raid or partition-table signatures (magic strings) from the specified device to make the signatures invisible for libblkid. The rheostat can also be mounted in the dash. ![]() It may also contain a rheostat (variable resistor) for adjusting the brightness of the instrument panel lights. It controls current flow to the bulbs in the headlamp system. ' Marker light The head/amp switch is an on/of s itch in the dash panel or on the steering column.Parking light Headlight [ Headlight Parking light lr.If the headlamps are concealed, the system also has either a vacuum or electric motor mechanism to operate the doors (faps) over the headlamps. Headlamp System The head/amp system includes the battery, headlamp wiri ng, fuse panel, light switch, dimmer switch, head- lamps (headlights), taillights, marker lights, and instru- ment lights. The interior lights normally include the dome light, instrument lights in the dash, trunk light, and other cour- tesy lights. The exterior lights typically include the headlights, turn signal lights, stoplights, parking lights, backup l ights, and side marker lights. As you will learn, actual vehicle lighting circuits are more complex than this. Figure 36-2 shows a simplifed drawing of a l ighting system. The exact circuit and part confgurations will vary with each make and model of vehicle. Lighting Systems The lighting system consists of the components (fuses, wires, switches, and relays) that operate the inte- rior and exterior lights on a vehicle. If you under- stand how these major parts function and fol low basic testing techniques, each system is relatively easy to fx. Bulbs, switches, relays, motors, fuses, and wiring can fail. 632 Section 5 Electrical Systems After prolonged use, the lighting, instrument, wiper, and horn circuits may require repairs. Note the location of the major components. Light, wiper, and other major electrical systems are simple when studied separately. Trunk light Backup light License plate light Taillight harness Taillight Engine harness compartment main harness Figure 36-1. They are installed on all passenger vehicles. These are essential systems that perform important safety functions. In this chapter, you will learn about the operation, basic testing, and repair of lighting, instrumentation, wiper, and horn circuits, Figure 36-1. Correctly answer ASE certifcation test questions on light, instrumentation, wiper, and hor systems. Summarize how to remove and service an instru- ment cluster. Multifunction switch Instrument panel/ dashboard Windshield washer harness motor Headlight assembly Parking and turn light Horn Windshield wiper motor Parking and turn light Lights, entation, WipeFs, and Horns- Operation and Service Explain both analog and digital instrumentation. Describe the safety practices to follow when working with l ight, wiper, and horn systems. Summarize automatic l ight and wiper systems. Diagnose proble1ns in l ight, wiper, and horn systems. After studying this chapter, you will be able to: Explain the operating principles of automotive l ight, wiper, and horn systems.
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