AUTOMOTIVE ELECTRICAL CIRCUITS AND WIRING

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2. NO-CHARGE INDICATOR (fig. 2-76) is set up to indicate whenever the alternator is not producing current. FUEL GAUGE Most fuel gauges are operated electrically and are composed of two units- the gauge, mounted on the instrument panel; and the sending unit, mounted in the fuel tank. The ignition switch is included in the fuel gauge circuit, so the gauge operates only when the ignition switch is in the ON position. Operation of the electrical gauge depends on either coil action or thermostatic action. The four types of fuel gauges are as follows: Figure 2-75.- Low voltage warning lamp schematic. Figure 2-76.- No-charge indiutor schematic. AUTOMOTIVE ELECTRICAL CIRCUITS AND WIRING 88/ 101
The THERMOSTATIC FUEL GAUGE, SELF-REGULATING (fig. 2-77), contains an electrically heated bimetallic strip that is linked to a pointer. A bimetallic strip consists of two dissimilar metals that, when heated, expand at different rates, causing it to deflect or bend. In the case of this gauge, the deflection of the bimetallic strip results in the movement of the pointer, causing the gauge to give a reading. The sending unit consists of a hinged arm with a float on the end. The movement of the arm controls a grounded point that makes contact with another point which is attached to an electrically heated bimetallic strip. The heating coils in the tank and the gauge are connected to each other in series. The THERMOSTATIC FUEL GAUGE, EXTERNALLY REGULATED (fig. 2-78), differs from a self-regulating system in the use of a variable resistance fuel tank sending unit and an external voltage-limiting device. The sending unit controls the gauge through the use of a rheostat (wire wound resistance unit whose value varies with its effective length). Theeffective length of the rheostat is controlled in the sending unit by a sliding brush that is operated by the float arm. The power supply to the gauge is kept constant through the use of a voltage limiter. The voltage limiter consists of a set of contact points that are controlled by an electrically heated bimetallic arm. The THERMOSTATIC FUEL GAUGE, DIFFERENTIAL TYPE (fig. 2-79), is similar to the other type of thermostatic fuel gauges, except that it uses two electrically heated bimetallic strips that share equally in operating and supporting the gauge pointer. The pointer position is obtained by dividing the available voltage between the two strips (differential). The tank unit is a rheostat type similar to that already described; however, it contains a wire-wound resistor that is connected between external terminals of one of the gauges of the bimetallic strip. The float arm moves a grounded brush that raises resistance progressively to one terminal, while lowering resistance to the other. This action causes the voltage division and resulting heat differential to the gauge strips formulating the gauge reading. The MAGNETIC FUEL GAUGE (fig. 2-80) consists of a pointer mounted on an armature. Depending upon the design, the armature may contain one or two poles. The gauge is motivated by a magnetic field that is created by two separate magnetic coils that are contained in the gauge. One of these coils is connected directly to the battery, producing a constant magnetic field. The other coil produces a variable field, whose strength is determined by a rheostat-type tank unit. The coils are placed 90 degrees apart. AUTOMOTIVE ELECTRICAL CIRCUITS AND WIRING 89/ 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
Page 37 and 38: If the ohmmeter reading is low or t
Page 39 and 40: After completing the required test
Page 41 and 42: CAUTION Follow the manufacturer's d
Page 43 and 44: armature and the field; the attract
Page 45 and 46: 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: operation, the voltage indicated on
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 and 98: AUTOMOTIVE WIRING Learning Objectiv
Page 99 and 100: Figure 2-86.- A typical wiring harn
Page 101: Figure 2-89.- Wiring diagram symbol
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AUTOMOTIVE ELECTRICAL CIRCUITS AND WIRING

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