AUTOMOTIVE ELECTRICAL CIRCUITS AND WIRING

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The TWO-WIRE CIRCUIT requires two wires to complete the electrical circuit- one wire from the source of electrical energy to the unit it will operate, and another wire to complete the circuit from the unit back to the source of the electrical power. Two-wire circuits provide positive connection for light and electrical brakes on some trailers. The coupling between the trailer and the equipment, although made of metal and a conductor of electricity, has to be jointed to move freely. The rather loose joint or coupling does not provide the positive and continuous connection required to use a ground return system between two vehicles. The two-wire circuit is commonly used on equipment subject to frequent or heavy vibrations. Tracked equipment, off-road vehicles (tactical), and many types of construction equipment are wired in this manner. WIRING ASSEMBLIES Wiring assemblies consist of wires and cables of definitely prescribed length, assembled together to form a subassembly that will interconnect specific electrical components and/ or equipment. The two basic types of wiring assemblies are as follows: The CABLE ASSEMBLY consists of a stranded conductor with insulation or a combination of insulated conductors enclosed in a covering or jacket from end to end. Terminating connections seal around the outer jacket so that the inner conductors are isolated completely from the environment. Cable assemblies may have two or more ends. WIRING HARNESS assemblies (fig. 2-86) serve two purposes. They prevent chafing and loosening of terminals and connections caused by vibration and road shock while keeping the wires in a neat condition away from moving parts of the vehicle. Wiring harnesses contain two or more individual conductors laid parallel or twisted together and wrapped with binding material, such as tape, lacing cord, and wire ties. The binding materials do not isolate the conductors from the environment completely, and conductor terminations may or may not be sealed. Wiring harnesses also may have two or more ends. WIRING IDENTIFICATION Wires in the electrical system should be identified by a number, color, or code to facilitate tracing circuits during assembly, troubleshooting, or rewiring operations. This identification should appear on wiring schematics and diagrams and whenever practical on the individual wire. The assigned identification for a continuous electrical connection should be retained on a schematic diagram until the circuit characteristic is altered by a switching point or active component. AUTOMOTIVE ELECTRICAL CIRCUITS AND WIRING 98/ 101
Figure 2-86.- A typical wiring harness. Wiring color codes are used by manufacturers to assist the mechanics in identifying the wires used in many circuits and making repairs in a minimum of time. No color code is common to all manufacturers. For this reason, the manufacturer's service manual is a must for speedy troubleshooting and repairs. Wiring found on tactical equipment (M-series) has no color. All the wires used on these vehicles are black. Small metal tags (fig. 2-87), stamped with numbers or codes, are used to identify the wiring illustrated by diagrams in the technical manuals. These tags are securely fastened near the end of individual wires. AUTOMOTIVE ELECTRICAL CIRCUITS AND WIRING 99/ 101
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AUTOMOTIVE ELECTRICAL CIRCUITS AND
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AUTOMOTIVE ELECTRICAL CIRCUITS AND
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It must help the charging system pr
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BATTERY CASE, COYER, AND CAPS. The
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BATTERY CAPACITY The capacity of a
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smaller charge is needed. As the ba
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the water slowly, stirring gently b
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the terminals just enough to secure
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Figure 2-6.- Battery leakage test.
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To perform a battery drain test, se
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must be used to convert from altern
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charge, the line voltage will incre
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Figure 2-14.- Schematic wiring diag
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short is present, the steel strip w
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Figure 2-20.- Testing an armature f
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The fingers on one of the claw-shap
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A cross-sectional view of a typical
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The electronic voltage regulators u
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If the ohmmeter reading is low or t
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After completing the required test
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CAUTION Follow the manufacturer's d
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armature and the field; the attract
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gears engage and when the engine ki
Page 47 and 48: voltage from the battery is often t
Page 49 and 50: eduction drive head may rotate as m
Page 51 and 52: Once the starter is checked and rep
Page 53 and 54: The ignition circuit is actually ma
Page 55 and 56: Figure 2-43.- Ignition switch and p
Page 57 and 58: DISTRIBUTOR CAP.- The distributor c
Page 59 and 60: SPARK PLUG WIRES The spark plug wir
Page 61 and 62: The components of an electronic ign
Page 63 and 64: As speed increases, centrifugal for
Page 65 and 66: Spark Plugs and Spark Plug Wires Ba
Page 67 and 68: Figure 2-50.- Ash fouled. When a sp
Page 69 and 70: A common problem arises when a CARB
Page 71 and 72: ELECTRONIC IGNITION DISTRIBUTOR SER
Page 73 and 74: After the initial ignition timing,
Page 75 and 76: Figure 2-56.-( A) Single-contact bu
Page 77 and 78: Figure 2-60.- Blackout light/ headl
Page 79 and 80: To ensure that the headlights are p
Page 81 and 82: Figure 2-65.- Blackout driving ligh
Page 83 and 84: The turn signal flasher unit (fig.
Page 85 and 86: EMERGENCY LIGHT SYSTEM The emergenc
Page 87 and 88: operation, the voltage indicated on
Page 89 and 90: The THERMOSTATIC FUEL GAUGE, SELF-R
Page 91 and 92: A pressure gauge is used widely in
Page 93 and 94: Figure 2-82.- Types of sending unit
Page 95 and 96: Electronic Speedometers and Tachome
Page 97: AUTOMOTIVE WIRING Learning Objectiv
Page 101: Figure 2-89.- Wiring diagram symbol
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AUTOMOTIVE ELECTRICAL CIRCUITS AND WIRING

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