AUTOMOTIVE ELECTRICAL CIRCUITS AND WIRING
AUTOMOTIVE ELECTRICAL CIRCUITS AND WIRING
AUTOMOTIVE ELECTRICAL CIRCUITS AND WIRING
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TESTING FIELD COILS.- To test the generator field, you must disconnect the<br />
grounded ends from the frame. Place one probe of the test lamp circuit on the field<br />
terminal end of the coils and the other probe on the grounded end. If the lamp lights,<br />
the field circuit is complete. However, because of the resistance in the field coil wire,<br />
it should not bum with normal brilliancy. Normal brilliancy of the test light bulb<br />
indicates a possible short circuit between the coils of the field. If the light does not<br />
burn, the field is open-circuited.<br />
A grounded field coil is located by placing one test probe on the field terminal and the<br />
other on the generator frame (fig. 2-16). If the test lamp lights, the field is grounded.<br />
The ground may be caused by frayed wires at the coil ends. In most cases, grounds and<br />
open field coil ends, the ohmmeter will measure the actual circuits in the field coils<br />
cannot be satisfactorily resistance of the coil. If the specified resistance of a repaired.<br />
The defective field coil must then be field coil is given in the manufacturer's manual,<br />
also replaced. obtained by measuring a new coil, you can compare values obtained<br />
through tests. For example, a short-Test for grounds, shorts, and open circuits in the<br />
circuited field coil would have practically no field coils can also be made with an<br />
ohmmeter. The resistance and the ohmmeter would register near zero; ohmmeter has<br />
test probes similar to the test lamp or the ohmmeter would register excessively high<br />
circuit. When these test probes are connected to the resistance in testing a coil having<br />
an open circuit. By following the manufacturer's instructions in using the ohmmeter,<br />
field coil tests can be made more quickly and accurately than by using a test lamp<br />
circuit.<br />
Figure 2-16.- Testing field coils for ground.<br />
ARMATURE TEST.<br />
There are two practical tests for locating shorts, opens, and grounds in armatures- the<br />
growler test and the bar-to-bar test.<br />
To test for short circuits, place the armature on the V-block of the growler and turn on<br />
the current. With a thin metal strip (hacksaw blade is good) held over the core, as<br />
shown in figure 2-17, rotate the armature slowly through a complete revolution. If a<br />
<strong>AUTOMOTIVE</strong> <strong>ELECTRICAL</strong> <strong>CIRCUITS</strong> <strong>AND</strong> <strong>WIRING</strong> 26/ 101