Alternator Voltage Regulator - TM-10-3930-627-120064

TM 10-3930-627-12

(2) If output is not as specified, replace

instead of the 13.6 to 14.3 volts given for the middle or

alternator.

"0" position.

Note. Additional tests and repairs are beyond

(4) If the actual regulating voltage as

checked is not within the voltage range specified for the

scope of equipment available at organizational

measured ambient temperature, replace the regulator.

maintenance. Refer defective alternators to direct or

(5) If the actual regulating voltage as

general support maintenance.

checked is within the voltage range specified for the

4-32. Alternator Voltage Regulator

measured ambient temperature, the charging system

a. Test.

operation is satisfactory. However, the voltage setting of

(1) Run engine at about 1500 rpm for 15

the regulator may need to be changed to meet the

minutes with spotlight on, and a thermometer placed

battery charging requirements for the type of driving

about 1/4 inch from the regulator cover.

being done. To properly adjust the voltage setting, refer

(2)

With engine running, connect a

to b below.

voltmeter to ground at the regulator base, and to either

b. Voltage Adjustment. To adjust the voltage

number 3 or number 4 terminal of the regulator (fig. 4-

regulator setting, remove the access plug from the

13). Compare temperatures and voltage reading with

regulator (fig. 4-14).

Then to correct for an

values given below in table 4-3 to learn if regulator is in

undercharged battery insert screwdriver into slot and turn

specified operating range.

clockwise one notch (0.3 volt) to increase the setting. To

correct for an overcharged battery, turn counterclockwise

one notch (0.3 volt) to decrease setting. Then check for

an improved battery condition over a service period of

reasonable length. If necessary, repeat the above

procedure for a higher or lower setting.

Note. Additional tests and adjustments of the

regulator are beyond the scope of equipment normally

available at organizational maintenance. If troubles are

not corrected, refer to direct or general support

maintenance.

Figure 4-13. Voltage regulator rest setup.

Table 4-3. Regulator Voltage Specifications

A+65 deg. F.

14.1 to 14.8 volts

A+85 deg. F.

13.9 to 14.7 volts

A+105 deg. F.

13.7 to 14.5 volts

A+125 deg. F.

13.6 to 14.3 volts

A+ 145 deg. F.

13.4 to 14.2 volts

(3) If actual voltage is not within the

specified range, remove access plug from regulator

cover (fig. 4-14) and note the position of the plastic

screw slot beneath the plug. The slot will be lined up

with one of the divisions or lines cast on the regulator

cover. For each division the slot has been moved

clockwise from the middle position ("0" position) or

toward the "+ " cast on the cover, add 0.3 volt to the

above specified range for the proper specified voltage

limits. For each division the slot has been moved

counterclockwise from the middle ("0" position) or toward

Figure 4-14. Regulator adjustment screw.

the "-" on the cover, subtract 0.3 volt from the above

specified range for the proper specified voltage limits.

c. Replacement. Unplug wiring harness from

As an example, assume that the slot is lined up with the

regulator, and remove mounting screws from base

second line from the "0" nearest the "+" mark. This

position would require adding of 0.6 volt to the

specification voltage shown in the specification table.

The limits at 1250 would become 14.2 to 14.9 volts

4-19