Test alternator output circuit as follows

ARMY TM 9-6115-464-34 AIR FORCE TO 35C2-3-445-2 NAVY NAVFAC P-8-624-34 (b) If voltage is zero, check fuse (11, figure 3-5). (c) If voltage is greater than zero, but below voltage VI in figure 3-8, check for poor circuit conditions between battery positive terminal and alternator positive output terminal. (d) Correct any discrepancies before proceeding with operational tests. (e) If voltage indicated is equal to voltage V1, test alternator negative output circuit as directed in step (5) below. (5) Test alternator output circuit as follows: (a) Check voltage V4 as indicated in figure 3-10. (b) lf voltage is below voltage at V1 (figure 3-8), check for inadequate circuit conditions between battery negative terminal and alternator negative output terminal. (c) Correct any discrepancies before conducting operational tests. (6) Conduct excitation voltage test as follows: (a) With voltmeter connected as in figure 3-11, close switch. (b) Voltmeter should indicate 3.5 ± 0.2 Vdc. (c) lf voltmeter indicates zero volts, test voltage regulator as directed instep (8) below. (d) lf voltmeter indication is greater than 3.7 Vdc, test for open circuit of alternator field (rotor) as directed in step (9) below. (e) lf voltmeter indication is as specified, proceed with voltage regulator, alternator output, and voltage protector test as outlined in step (10) below. (7) Test for faulty alternator voltage regulator as follows: (a) (b) (c) (d) (e) (f) (g) (h) (i) Remove screws (1, figure 3–5) and cover assembly (2). Disconnect voltage regulator by disconnecting and tagging the red, green and black leads. Disconnect and tag the blue and yellow output leads. Install a jumper from the GND terminal to brush terminal as shown in figure 3-12. Install alternator in test circuit as shown in figure 3-12. N O T E A means of rotating the alternator at 2000 to 3000 RPM must be provided. This test can be performed with the alternator installed on an operational generator set, and operating the set at rated frequency. With the alternator rotating at 2500 RPM the voltmeter should indicate 24 to 28 volts and the ammeter should indicate 32 to 35 amperes. If the alternator tests satisfactorily, this indicates that the voltage regulator was faulty. If the alternator does not test satisfactorily, this indicates that the voltage regulator is good and the trouble is in the alternator. If the regulator is faulty, remove the jumper (figure 3-12) and install a new regulator and cover assembly using the tagged leads on the old cover assembly as a guide when making connections. (8) Conduct field current test as follows: 3-23