1. FIGURE 21-1 The digital multimeter should be set to read DC volts, with the red lead connected to the positive (+) battery terminal and the black meter lead connected to the negative (-) battery terminal.

2. FIGURE 21-2 A scan tool such as this Chrysler DRB III can be used to check the generator output voltage.

3. FIGURE 21-3 If the rear bearing is magnetized, the voltage regulator, generator brushes, and rotor are functioning.

4. FIGURE 21-4 A GM generator with an internal voltage regulator can be identified by the horizontal plug-in connector.

5. FIGURE 21-5 Connections required to full-field a GM generator with an external voltage regulator.

6. FIGURE 21-6 Connections required to full-field a Ford generator with an external voltage regulator.

7. FIGURE 21-7 Jumper wire connections required to full-field a Ford (or Leece-Neville) generator with an internal electronic voltage regulator.

8. FIGURE 21-8 Wiring diagram of a Ford integral generator or regulator (IAR) assembly.

9. FIGURE 21-9 Connections required to full-field a Chrysler generator with a mechanical voltage regulator.

10. FIGURE Connections required to full-field a Chrysler generator with an electronic voltage regulator.

11. FIGURE Charging system voltage can be easily checked at the lighter plug by connecting a lighter plug to the voltmeter through a double banana plug.

12. FIGURE Before replacing a generator (alternator), the wise technician checks that battery voltage is present at the output and battery voltage sense terminals.

13. FIGURE This accessory drive belt should be replaced because it has many cracks. The usual specification for when a serpentine belt requires replacement is when there are three or more cracks in any one rib in any 3 in. length.

14. FIGURE AC ripple at the output terminal of the generator is more accurate than testing at the battery due to the resistance of the wiring between the generator and the battery. The reading shown on the meter is only 78 mV (0.078V),far below what the reading would be if a diode were defective. (Courtesy of Fluke Corporation)

15. FIGURE A mini clamp-on digital multimeter can be used to measure generator output. This meter was set on the 200-A DC scale. With the engine running and all lights and accessories on, the generator was able to produce almost exactly its specified rating of 105 A.

16. FIGURE 21-16 Voltmeter hookup to test the voltage drop of the charging circuit.

17. FIGURE 21-17 Typical GM SI generator
FIGURE Typical GM SI generator. Note the location and wire color used for terminals 1 and 2.

18. FIGURE 21-18 Typical GM CS generator wiring plug identification
FIGURE Typical GM CS generator wiring plug identification. Note that terminal F is sometimes terminal I on some generators.

19. FIGURE 21-19 Typical hookup of a starting and charging tester.

20. FIGURE The output rating on the General Motors generator (alternator) is stamped into the case.

21. FIGURE 21-21 The output on this generator is printed on a label.

22. FIGURE When connecting an inductive ammeter probe, be certain that the pickup is over all wires. The probe will work equally well over either all positive or all negative cables because all current leaving a battery must return.

23. FIGURE A diagram showing the location of the charging system wiring of a typical vehicle. The best location to use to check for the generator alternator) output is at the output wire from the B+ (BAT) terminal. Notice that the generator supplies all electrical needs of the vehicle first, then charges the battery if needed.

24. FIGURE Always mark the case of the generator before disassembly to be assured of correct reassembly.

25. FIGURE 21-25 Explanation of clock positions
FIGURE Explanation of clock positions. Because the four through bolts are equally spaced, it is possible for a generator to be installed in one of four different clock positions. The connector position is determined by viewing the generator from the diode end with the threaded adjusting lug in the up or 12 o’clock position. Select the 3 o’clock, 6 o’clock, 9 o’clock, or 12 o’clock position to match the unit being replaced.

26. FIGURE 21-26 Testing a generator rotor using an ohmmeter.

27. FIGURE If the ohmmeter reads infinity between any two of the three stator windings, the stator is open and, therefore, defective. The ohmmeter should read infinity between any stator lead and the steel laminations. If the reading is less than infinity, the stator is grounded. Stator windings can be tested if shorted because the normal resistance is very low.

28. FIGURE 21-28 An open in a delta-wound stator cannot be detected using an ohmmeter.

29. FIGURE 21-29 Typical diode trio
FIGURE Typical diode trio. If one leg of a diode trio is open, the generator may produce close to normal output, but the charge indicator light on the dash will be on dimly. The plus signs indicate the anodes, and the minus sign indicates the cathode terminal of the diodes.

30. FIGURE 21-30 A GM rectifier bridge that has been disassembled to show the individual diodes.

31. FIGURE 21-31 Diodes being soldered to the stator on a Ford generator.

32. FIGURE Testing a GM SI internal voltage regulator using a voltage regulator tester. This tester can be used to test most internal and external electronic voltage regulators by using the appropriate adapter harness and test leads.

33. FIGURE 21-33 A brush holder assembly shown assembled in the generator
FIGURE A brush holder assembly shown assembled in the generator. The brush retainer is actually a straightened-out paper clip.

34. FIGURE 21-34a A generator for a GEO Prism looks like a typical General Motors CS-130 except for this adapter that converted the Toyota wiring harness to the GM generator.

35. FIGURE 21-34b After removing the adapter, the original generator connection is visible.