Automotive Electrical & Electronic Systems Classroom Manual

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Shielding Metal Shields, such as the ones used in breaker point distributors, block the waves from components that create RFI signals. The circuits of onboard computers are protected to some degree from external electromagnetic waves by their metal housings.

Ground Straps Ground or bonding straps between the engine and chassis of an automobile help suppress EMI conduction and radiation by providing a low-resistance circuit ground path. Such suppression ground straps are often installed between rubber-mounted components and body parts, Figure 4-36. On some models ground straps are installed between body parts, such as the hood and a fender panel where no electrical circuit exists, Figure 4-36. In such a case, the strap has no other job than to suppress EMI. Without it, the sheet-metal body and hood could function as a large capacitor. The space between the fender and hood could form an electrostatic field and couple with the computer circuits in the wiring harness routed near the fender panel. For more information about ground straps, see the section on “Diagnostic Strategies” in Chapter 4 of the Shop Manual.

EMI Suppression Interference suppression is now a critical automotive engineering task because the modem automobile has an increased need for EMI suppression.

Figure 4-36. Ground straps are installed in many areas of the engine compartment to suppress EMI. (Reprinted by permission of Robert Bosch GmbH)

Chapter Four

The increasing use of cellular telephones, as well as onboard computer systems, are only two of the factors that have made interference suppression extremely important. Even small amounts of EMI can disrupt the operation of an onboard digital computer, which operates on voltage signals of a few millivolts (thousandths of a volt) and milliamperes (thousandths of an ampere) of current. Any of the interference transmission modes discussed earlier are capable of creating false voltage signals and excessive current in the computer systems. False voltage signals disrupt computer operation, while excessive current causes permanent damage to micro-electric circuitry. As the complexity and number of electronic systems continues to increase, manufacturers are using multiplex wiring systems to reduce the size and number of wiring harnesses, which also reduces EMI. Multiplexing is a method of sending more than one electrical signal over the same channel.

SUMMARY Electricity can be generated in several ways. The most important way for automotive use is by magnetism. Magnetism is a form of energy caused by the alignment of atoms in certain materials. It is indicated by the ability to attract iron. Some magnetic materials exist in nature; others can be artificially magnetized. The magnetic properties of some metals, such as iron, are due to electron motion within the atomic structure. Reluctance is resistance to the movement of magnetic lines of force: iron cores have permeability and are used to reduce reluctance in electromagnetic fields. Lines of force, called flux lines, form a magnetic field around a magnet. Flux lines exit the north pole and enter the south pole of a magnet. Magnetic flux lines also surround electrical conductors. As current increases, the magnetic field of a conductor becomes stronger. Voltage can be generated by the interaction of magnetic fields around conductors. The relative movement of a conductor and a magnetic field generates voltage. This process is called induction. Either the conductor or the magnetic field may be moving. The strength of the induced voltage depends on the strength of the magnetic field, the number of conductors, the speed of the relative motion, and the angle at which the conductors cut the flux lines. Electromagnetic induction is used in generators, alternators, electric motors, and coils. Magnetomotive force (mmf) is a


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Summary

4min
page 363

Cruise Control Systems

3min
pages 357-358

Review Questions

3min
pages 364-366

Radios and Entertainment Systems

6min
pages 337-339

Theft Deterrent Systems

7min
pages 353-356

Heated Seats

6min
pages 343-345

Power Seats

2min
pages 341-342

Power Door Locks, Trunk Latches, and Seat- Back Releases

2min
page 346

Heating and Air-Conditioning Systems

12min
pages 328-334

Class 2 IPM-Controlled HVAC Systems

2min
pages 335-336

Review Questions

1min
page 326

Summary

1min
page 325

Windshield Wipers and Washers

10min
pages 319-324

Summary

1min
page 314

Review Questions

2min
pages 315-316

Head-Up Display (HUD

5min
pages 311-313

Electromagnetic Instrument Circuits

11min
pages 296-300

Review Questions

2min
pages 293-294

Malfunction Indicator Lamp (MIL

5min
pages 301-303

Summary

1min
page 292

Instrument Panel and Interior Lamp Circuits

4min
pages 289-291

Circuits

1min
page 288

Backup Lamp Circuits Side Marker and Clearance Lamp

1min
page 287

Circuits

2min
page 286

Stop Lamp and Turn Signal Circuits Hazard Warning Lamp (Emergency Flasher)

6min
pages 282-285

Taillamp, License Plate Lamp, and Parking Lamp Circuits

1min
page 281

Common Automotive Bulbs

1min
page 280

Headlamp Circuits

16min
pages 270-279

Summary

1min
page 267

Review Questions

1min
page 268

Spark Plug Construction

4min
pages 264-266

Distributor Cap and Rotor

3min
pages 259-261

Primary and Secondary Circuits

1min
page 248

Voltages

4min
pages 246-247

Basic Circuits and Current

1min
page 241

Silicon-Controlled Rectifiers (SCRs

1min
page 233

Review Questions

2min
pages 236-238

Summary

1min
page 235

Transistors

9min
pages 229-232

Rectifier Circuits

2min
page 228

Semiconductors

7min
pages 222-224

Photonic Semiconductors

2min
page 227

Review Questions

3min
pages 218-220

Starter Motor and Drive Types

8min
pages 210-214

DC Starter Motor Operation

5min
pages 206-208

Summary

2min
pages 216-217

Overrunning Clutch

1min
page 215

Specific Starting Systems

6min
pages 200-203

Summary

2min
pages 191-192

Differences

13min
pages 183-190

Review Questions

3min
pages 193-194

Charge/Voltage/Current Indicators

3min
pages 180-181

Solid-state Regulators

9min
pages 175-179

Electromagnetic Regulators

1min
page 174

Voltage Regulation

2min
page 173

Current Production in an AC Generator

9min
pages 168-172

Diode Rectification

3min
pages 162-163

AC Generator (Alternator) Components

7min
pages 164-167

Review Questions

4min
pages 157-158

Battery Installations

4min
pages 150-151

Battery Installation Components

2min
pages 152-153

Summary

2min
page 156

Battery Life and Performance Factors

5min
pages 154-155

State-of-Charge Indicators Wet-Charged and Dry-Charged

2min
page 147

Battery Electrolyte

2min
page 146

Electrochemical Action

8min
pages 142-145

Review Questions

3min
pages 138-140

Wire Color Coding

2min
pages 121-122

Multiplex Circuits

8min
pages 112-114

Ground Paths

2min
page 111

Connectors and Terminals

5min
pages 108-110

Wire Size

6min
pages 105-107

Wire Types and Materials

2min
page 104

Wiring and Harnesses

2min
pages 102-103

Review Questions

4min
pages 97-100

Parallel Circuit Voltage Drops Calculating Series Circuit Total

1min
page 87

Series and Parallel Circuit Faults

3min
pages 94-95

Series-Parallel Circuits

4min
pages 91-93

Review Questions

2min
page 82

Summary

3min
pages 80-81

Electromagnetism

9min
pages 67-71

Electromagnetic Induction

11min
pages 72-76

Magnetism

2min
page 66

Power

2min
page 56

Capacitance

8min
pages 57-60

Review Questions

2min
pages 62-64

Summary

1min
page 61

Complete Electrical Circuit

3min
pages 52-53

Summary

2min
page 43

Historical Figures in Electricity

2min
page 42

Fire Extinguishers

1min
page 31

Safety Tips for Technicians

2min
pages 25-26

Nuts

1min
page 15

Review Questions

2min
pages 44-46

Electrical Cord Safety

1min
pages 29-30

Safety in Lifting (Hoisting) a Vehicle

2min
pages 27-28
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