Test and adjust the current regulator as

TM 10-3930-632-12

CAUTION

(b) Gradually increase the speed of

the alternator until the relay contacts close. Note the

Make sure the ends of the leads are

voltage; it should be between 11.8 and 13.5 volts. If the

insulated from the ground at all times to

closing voltage is not within this range, adjust by turning

avoid a short circuit.

the adjusting screw on top of the cutout relay.

(b) Cycle the alternator as directed in

CAUTION

subparagraph (3). With the alternator operating at 4000

Cycle the alternator before each test and

RPM and the regulator at operating temperature, note

adjustment by reducing the alternator speed

the voltage registered on the voltmeter; it should be as

until the cutout relay opens; then increase

indicated in table 4-3. If the voltage is not within this

the speed slowly until the proper speed for

range, adjust by turning the adjusting screw at the back

testing is reached.

of the voltage regulator. Cycle the alternator after each

(4) Test and adjust the voltage regulator

change or adjustment.

as follows:

(5) Test and adjust the current regulator as

(a) Measure the voltage regulator

follows:

airgap. Push the armature down until the points open;

(a) Measure the airgap of the current

release until the points barely close. Measure the airgap

regulator by the same method used to measure the

at the point between the armature and the part of the

airgap of the voltage regulator in subparagraph (4) (a).

core next to the residual pin. The airgap should be

This airgap between the armature and that part of the

0.075 inch. Adjust by loosening the contact mounting

core next to the residual pin should be 0.075 inch.

screws, inserting a 0.075-inch thick flat gage in the

Adjust the airgap by loosening the contact mounting

airgap. Position the contacts so they barely touch;

screws and positioning the contact. Tighten the screws

secure the contact mounting screws. Connect the

after the proper setting is obtained.

regulator as shown in figure 4-17.

(b) Test the current regulator setting

by connecting the regulator as shown in figure 4-18.

Prevent voltage regulator from operating during the test

by connecting a carbon pile load of approximately the

same value as the current regulator setting across the

battery terminals during the time the current regulator

setting test is made. When the alternator output is

increased to maximum, the current should be as shown

in table 4-3. If the amperage is not within this range,

adjust by rotating screw at the back of the current

regulator. After each change of adjustment, reduce the

alternator speed until the cutout relay opens; then return

to speed and check the current indication on the

ammeter.

Figure 4-17. Voltage Regulator Setting Test Circuit

Figure 4-18. Current Regulator Setting Test Circuit

4-33