AUTOMOTIVE ELECTRICAL CIRCUITS AND WIRING

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TESTING FIELD COILS.- To test the generator field, you must disconnect the grounded ends from the frame. Place one probe of the test lamp circuit on the field terminal end of the coils and the other probe on the grounded end. If the lamp lights, the field circuit is complete. However, because of the resistance in the field coil wire, it should not bum with normal brilliancy. Normal brilliancy of the test light bulb indicates a possible short circuit between the coils of the field. If the light does not burn, the field is open-circuited. A grounded field coil is located by placing one test probe on the field terminal and the other on the generator frame (fig. 2-16). If the test lamp lights, the field is grounded. The ground may be caused by frayed wires at the coil ends. In most cases, grounds and open field coil ends, the ohmmeter will measure the actual circuits in the field coils cannot be satisfactorily resistance of the coil. If the specified resistance of a repaired. The defective field coil must then be field coil is given in the manufacturer's manual, also replaced. obtained by measuring a new coil, you can compare values obtained through tests. For example, a short-Test for grounds, shorts, and open circuits in the circuited field coil would have practically no field coils can also be made with an ohmmeter. The resistance and the ohmmeter would register near zero; ohmmeter has test probes similar to the test lamp or the ohmmeter would register excessively high circuit. When these test probes are connected to the resistance in testing a coil having an open circuit. By following the manufacturer's instructions in using the ohmmeter, field coil tests can be made more quickly and accurately than by using a test lamp circuit. Figure 2-16.- Testing field coils for ground. ARMATURE TEST. There are two practical tests for locating shorts, opens, and grounds in armatures- the growler test and the bar-to-bar test. To test for short circuits, place the armature on the V-block of the growler and turn on the current. With a thin metal strip (hacksaw blade is good) held over the core, as shown in figure 2-17, rotate the armature slowly through a complete revolution. If a AUTOMOTIVE ELECTRICAL CIRCUITS AND WIRING 26/ 101
short is present, the steel strip will become magnetized and vibrate. To find out whether the armature coils of the commutator are short-circuited, clean between the commutator segments and repeat the test. Should the thin metal strip still vibrate, the armature is short-circuited internally and must be replaced. Not all armatures can be tested for short circuits by the method just described. These armatures can be identified by excessive vibration of the saw blade all around the armature during the test. With these armatures, test for short circuits by using the milliampere contacts on an ac millimeter, as shown in figure 2-18. In doing so, keep the armature stationary in the V-block and move the contacts around the commutator until the highest reading is obtained. Then turn the armature to bring each pair of segments under the contacts and read the milliammeter at the same time. The readings should be nearly the same for each pair of adjacent bars. If a coil is short-circuited, the milliammeter reading will drop to almost zero. Figure 2-17.- Using an armature growler. Test the armature for grounds by using the test light circuit, which is a part of most modern factory-built growlers (fig. 2-19). Place the armature on the V-block and touch one of the test probes to the armature core iron. Touch the other probe to each commutator segment in turn. If the armature is grounded, the bulb in the base of the growler will light. In contacting armature surfaces with the test probes, do not touch the bearing or the brush surfaces of the commutator. The arc would burn or pit the smooth finish. Replace the armature if it is grounded. AUTOMOTIVE ELECTRICAL CIRCUITS AND WIRING 27/ 101
Page 1 and 2: AUTOMOTIVE ELECTRICAL CIRCUITS AND
Page 3 and 4: AUTOMOTIVE ELECTRICAL CIRCUITS AND
Page 5 and 6: It must help the charging system pr
Page 7 and 8: BATTERY CASE, COYER, AND CAPS. The
Page 9 and 10: BATTERY CAPACITY The capacity of a
Page 11 and 12: smaller charge is needed. As the ba
Page 13 and 14: the water slowly, stirring gently b
Page 15 and 16: the terminals just enough to secure
Page 17 and 18: Figure 2-6.- Battery leakage test.
Page 19 and 20: To perform a battery drain test, se
Page 21 and 22: must be used to convert from altern
Page 23 and 24: charge, the line voltage will incre
Page 25: Figure 2-14.- Schematic wiring diag
Page 29 and 30: Figure 2-20.- Testing an armature f
Page 31 and 32: The fingers on one of the claw-shap
Page 33 and 34: A cross-sectional view of a typical
Page 35 and 36: 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
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The turn signal flasher unit (fig.
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EMERGENCY LIGHT SYSTEM The emergenc
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operation, the voltage indicated on
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The THERMOSTATIC FUEL GAUGE, SELF-R
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A pressure gauge is used widely in
Page 93 and 94:
Figure 2-82.- Types of sending unit
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Electronic Speedometers and Tachome
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AUTOMOTIVE WIRING Learning Objectiv
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Figure 2-86.- A typical wiring harn
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Figure 2-89.- Wiring diagram symbol
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AUTOMOTIVE ELECTRICAL CIRCUITS AND WIRING

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