Electrical Components - PowerPoint Presentation

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Electrical Components

Instructor Name: (Your Name)

4

CHAPTERSlide2

Learning ObjectivesDescribe the components that make up a truck wiring harness

Repair a damaged section of wireDetermine the correct wire gauge to be used based on the amperage and length of the conductorDescribe the different types of electrical switches using terms such as poles, throws, normally open, and momentary contactSlide3

Learning Objectives (continued)

Use a voltmeter to determine if a switch is open, closed, or defectiveDefine the function of each terminal of a standard ISO relayTroubleshoot a circuit controlled by a relay and list the most likely failures of a relayExplain how circuit protection devices (CPD’s) operate and the importance of replacing a CPD with the rating specified by the OEMSlide4

Learning Objectives (continued)

Use a voltmeter to determine if a CPD is openLocate an open circuit and shorted to ground circuit, using wiring schematics and electric test toolsSlide5

Wiring Harnesses

A wiring harness is a modularized section of wires designed to be connected to electrical components and other wiring harnessesConnectors are interlocking devices that permit connections to electrical components or wiring harnessesTerminals are electrically conductive pins (male) and sockets (female) that provide electrical connections between two connectorsSlide6

Typical Wiring Harness

Figure 4-1 Typical wiring harness.Slide7

Tech Tip

You may find that one or more terminals may be missing in a multi-terminal connector that has been exposed to road salt mixed with water, while the other terminal may only have a small amount of corrosion. Terminal in the connectors supplied with constant battery power can dissolve in a brief amount of time when exposed to salt water.Slide8

Wire DetailsStranded wire, wire made up of several smaller-diameter wires, is the most common found in use in trucks

Wire diameter is most commonly measured by the American Wire Gauge (AWG) or International Organization Standardization (ISO)Wire size is the actual conductor not including the insulatorSlide9

Stranded Wire

Figure 4-2 Stranded wire.Slide10

Wire Details (continued)

The smaller the AWG number gets the larger the wire diameter getsCable is often used to describe large-diameter wiresISO metric wiring indicates the cross- sectional area of the wire in mm²The larger the ISO rating the larger the wire diameterSlide11

AWG and ISO Wire Sizes

Figure 4-3 AWG and metric ISO wire sizes.Slide12

Wire Details (continued)

The resistance of a wire decreases as the diameter increases The resistance of a wire increases as the length of the wire increasesBecause resistance increases with length, it may be necessary to increase the wire gauge for loads that are a long distance for the voltage sourceAutomobiles often use polyvinyl chloride material as an insulatorMost insulators are color coded to provide circuit identification on the vehicleSlide13

Chassis Ground

Current needs a path from the positive terminal of the battery through electrical device and back to the negative terminal of the batteryThe negative terminal of the battery is connected to the steel frame rails providing the return pathWhen the negative battery terminal is connected to the frame rail it is said to have a negative groundWith a negative ground system, only a positive wire is needed from the batterySlide14

Typical Chassis Ground Symbols

Figure 4-6 Chassis or frame ground symbols: a low-resistance circuit is assumed. Slide15

Flexible Conduit Protects Wire Insulation from Abrasion

Figure 4-7 Flexible conduit protects wire insulation from abrasion.Slide16

Wiring Harness Repairing

Standard compress or crimp type butt connectors are fast Heat-shrinkable butt connectors are preferableTerminals come in three color coded sizes; red, blue, and yellowSoldering wires, then covering with a heat shrinkable tubing, is the preferred method for repairing if time allowsPlastic or electricians tape is

not acceptable for sealing wiring repairs outside the cabSlide17

Crimp-Type Butt Connectors With Heat-Shrinkable Insulation

Figure 4-8 Crimp-type butt connectors with heat-shrinkable insulation.Slide18

Connectors and TerminalsMolded connectors

contain terminals molded in a rubber or soft plastic material.Molded terminals are often designed to mate with a specific device or component.Hard shell connectors contain 1 to 80 terminals. Hard shell connectors are used to provide interconnections between wiring harnesses and electronic control modules.Slide19

Sealed Connectors

Figure 4-11 Hard-shell connector body.

Figure 4-12 Individual wire seals installed before crimping terminals to wire end.

Figure 4-13 Multi-wire connector seal.Slide20

Crimping Terminals

Figure 4-14 Terminal crimping tool.

Figure 4-15 Wire end and terminal before and after crimping operation.Slide21

Installing Terminals

Figure 4-17 Wire with terminal and individual seal is inserted into connector body.

Figure 4-19 Pull-to-seat terminals: terminal is crimped to wire end after inserting wire end into connector body and seal.Slide22

Installing Terminals (continued)

Figure 4-20 Pulling the terminal to seat into place in the connector body after terminal is crimped to wire end.

Figure 4-21 Special terminal extracting tools.Slide23

Switches

When a switch is on it is closedWhen a switch is off it is openThe two pieces of a switch that actually make or break current are known as contactsPoles describe the number of input terminal a switch hasThrow describes the number of positions a switch can be moved to and still complete a circuitThe terms pole and throw are used together to describe the basic functionality of a switchSlide24

Knife Switch

Figure 4-22 Knife switch.Slide25

Switch Types

Figure 4-23 Single-Pole Single-Throw (SPST)Figure 4-24 Double-Pole Single-Throw (DPST)Figure 4-25 Single-Pole Double-Throw (SPDT)Slide26

Switches (continued)

Latching switches remain in the position they are placed inMomentary contact switches open or close the circuit as long as the user holds the switchThe normal state of a momentary switch is the contact position when the switch is not activatedNC = normally closedNO = normally openSlide27

Figure 4-28

Voltage drop across closed and open switch.Slide28

Switch Troubleshooting

Figure 4-30High resistance switch.Figure 4-31Open circuit before switch.Figure 4-32Open circuit after switch.Slide29

Relay Components

Figure 4-33 Relay components.Slide30

Terminal Designation and Function of a ISO or DIN Relay

85 and 86 – Coil terminal, normally 50Ω to 100Ω of resistance between them30 – Common terminal. Normally connected to power source.87 – Normally open terminal. When the relay is energized the 30 and 87 terminal will close87A – Normally closed terminal. When the relay is energized the 30 and 87A terminal will openSlide31

ISO or DIN Relay Terminals and Footprint

Figure 4-34 Common relay terminals and footprint.Slide32

Typical Relay Contact Schematics

Figure 4-35 Typical relay contact schematics.Slide33

Larger Relays

Figure 4-38 Components of a magnetic (mag) switch.Slide34

Circuit Protection Devices

Circuit protection devices (CPD) primary purpose in a truck is to protect the wiring harnessCPD’s include fuses, circuit breakers, fusible links, and positive coefficient devicesCPD’s allow current flow up to the current rating then melt and open the circuitOEM’s select current rating based on the smallest wire in the circuit being protectedSlide35

Circuit Protection Devices

Any additional wiring added to a truck should be protected by a CPDNever replace a wire with a wire of smaller diameterSome CPD’s are designed to open more slowly or more quickly then others to permit inrush currentCommon causes for excessive current flow in a circuit are excess current drawing devices or a short to groundAlways replace a CPD with the OEM recommended ratingSlide36

Typical Automotive Fuses

Figure 4-41 Blown or Open FusesFigure 4-42 Automotive Type FusesSlide37

Circuit Breakers

Circuit breakers are a form of CPD’sCircuit breakers have thin bi-metal strips that when heated bend or snap and open the circuitAn open circuit breaker is considered trippedWhen the circuit breaker cools it resetsThere are three SAE classifications of circuit breakers; Type I, II and IIISlide38

Circuit Breakers (continued)

Type I circuit breakers automatically reset after they cool downType II circuit breakers automatically reset after the cause of the excess current draw is no longer presentType III circuit breakers manually reset after the excess current draw is no longer present and the bimetal strip coolsSlide39

Type I, II, And III Circuit Breakers

Figure 4-48 Type IFigure 4-50 Type III (A) and Type II (B).Slide40

Application of Circuit Protection Devices

Figure 4-53 Figure 4-54One fuse protecting several circuits. One fuse for each parallel branch.Slide41

Typical Truck CPD Layout

Figure 4-55 Typical truck CPD layout.Slide42

Terminology for Wiring Problems

Open circuit - a circuit with high or infinite circuit resistance, which results in reduced or interrupted current flow in the circuitShort to ground – occurs when the conductor in a circuit has an unwanted contact with groundShort to battery positive - occurs when the conductor in a circuit has an unwanted contact with positive voltage sourceWire to wire short – Occurs when the conductor in a circuit has unwanted contact with another wire Slide43

Types of Wiring Defects

Figure 4-57 Types of wiring defects: (A) Open circuit, (B) short to ground, (C) short to battery positive, (D) wire to wire short.Slide44

Basic Electrical / Electronic Diagnostic Procedure Flowchart

Figure 4-48 Diagnostic flowchart.Slide45

Common Wiring Diagram Schematic Symbols

Figure 4-59 Common wiring diagram schematic symbols.Slide46

Fuse Wiring Diagram For Heated Mirrors and Back-up Lamps

Figure 4-60 Fuse wiring diagram indicating fuse F5 supplies the mirror heat and back-up lamp circuits.Slide47

Using Peak Hold to Find Intermittent Short

Figure 4-63 Using peak hold with DMM ohmmeter to find intermittent short.Slide48

Test Light Indicating Presence of Voltage

Figure 4-65 Test light indicating presence of voltage.Slide49

Normal Voltage Readings

Figure 4-66 Circuit with no defects, open switch and closed switch.Slide50

SummaryTruck wiring is divided into a series of sections called harnesses. Harnesses are mated using connectors. Connectors contain terminals the provide the electrical contact between sections of

wire.Wire diameter for North American - built trucks is typically defined by the AWG number. The smaller AWG number, the larger the wire diameter.Slide51

Summary (continued)

Wire has resistance. The resistance of wire is directly proportional to the wire length and inversely proportional to the wire diameter.The frame rails, sheet metal, and other metal components of a typical truck are called chassis ground. The negative battery terminal is connected to the chassis ground. The chassis ground acts as a conductor for many truck electrical circuits.Slide52

Summary (continued)

Wiring harness routing refers to the placement of a wiring harness on a truck. Clipping is the attachment method used to attach the harness to the truck.Electric switches are devices used to interrupt the flow of current in a circuit. There are many types of switches. The functionality of a particular switch can be defined by the terms pole and throw.Slide53

Summary (continued)

Normal state of a switch describes momentary contacts that are open or closed when the switch is not depressed or otherwise disturbed. A normally closed switch has continuity until the switch is depressed. A normally open switch has continuity only when the switch is depressed.A closed switch should have close to 0V drop across it; an open switch should have near battery voltage drop across it.Slide54

Summary (continued)

Relays are electromagnetic switching devices. A small amount of current flow through a coil forms an electromagnet. The electromagnet causes the relay contacts to open or close, in much the same way as a switch. A relay is like a remotely controlled switch.Relay control circuit describes the electrical circuit that powers the relay. When a positive voltage source and ground are provided by the relay control circuit, the relay coil is energized. Slide55

Summary (continued)

Circuit protection devices are designed to protect the truck’s wiring harness. Circuit protection devices include fuses, circuit breakers, and fusible links.Inrush or surge describes the high level of current that is drawn by some devices for a brief period of time when first switch on, such as motors and light bulbs. Surge current may be many times greater than the normal current drawn by a device after a brief period of time. Slide56

Summary (continued)

Adding additional loads such as lights to a circuit causes the current through the circuit protection device to increase. Never replace a circuit protection device with one that has a higher rating than the OEM’s recommendation.Fuses are single use devices that have an element designed to open when the current flow through the fuse exceeds the fuse rating. A combination of time and current cause the element to open.Slide57

Summary (continued)

Circuit breakers use a bimetal strip to open a set of normally closed contacts. The three main classes of circuit breakers are SAE Type I, Type II, and Type III.Fusible links are made of wire with a special insulated material designed not to burn. The fusible link is designed to be the smallest wire gauge in the circuit that it is protecting.