(1)
(2)
(3)
(4)
(5)
(6)
If the FL-NL or NL - FL transient exceeds 1-1/2 percent of rated speed and/or does not
reestablish stable engine operating conditions within one second, realign the control unit in
accordance with paragraph 3-64j. Also follow this procedure if the engine speed hunts. If the set
cannot be stabilized, check sockets A and B of plug P-21 (figure 3-97) for 24 Vdc (A is positive).
If the engine speed increases to above nominal operating speed, check sockets A and B of P-17
(figure 3–97) for 120 Vac. If it is missing, troubleshoot the generator set wiring. Refer to schematic
and troubleshooting diagram plates located on inside of left and right engine compartment doors
(figure 3-97). If it is present, check the resistance of the frequency adjusting circuit consisting of R4
(250 ohms) rheostat R1 frequency adjust (500 ohms) and R6 (250 ohms) fixed resistor. Measure the
total circuit resistance across N and T of harness plug PI 7 (figure 3-97). The circuit resistance
should be 1000 ohms (5 percent tolerance). After testing for correct total resistance, test the
operation of the frequency adjust rheostat by connecting an ohmmeter across pins M and T and
revolving the frequency adjust rheostat through its entire travel. The resistance should vary from 750
ohms to 250 ohms. Repeat this procedure using the ohmmeter across pins M and N of the harness
plug. If the problem persists, check sockets A and B of plug P-21 (figure 3-97) for 24 Vdc (A is
positive).
If the engine speed remains below the nominal operating speed, adjust RI. If there is no
improvement, check the resistance of the frequency adjust circuit. Disconnect P–17 and check the
resistance of the frequency adjust circuit consisting of R4 (250 ohms) fixed resistor, RI frequency
adjust rheostat (500 ohms) and R5 (250 ohms, 5 percent) fixed resistor. Measure the total circuit
resistance across N and T of harness plug P-17. The circuit resistance should be 1000 ohms (5
percent tolerance). After testing for correct total resistance, test the operation of the frequency adjust
potentiometer by connecting an ohmmeter across pins M and T and revolving the travel. The
resistance should vary from 750 ohms to 250 ohms. Repeat this procedure using the ohmmeter
across pins M and N of the harness plug. Disconnect actuator electrical connector before making this
measurement. Push actuator piston all the way down and adjust engine speed with manual throttle.
If this value resistance is measured, check sockets A and Bat plug P–21 for 24 Vdc (A is positive).
If the set is operating at a constant load and voltage and during an eight–hour period the change in
ambient temperature does not exceed 60°F, the set frequency should not drift beyond 1/2 of one
percent of rated frequency. The above requirement assumes that the set temperatures were
stabilized at the initial and final ambient temperatures.
NOTE
If the drift in paragraph (4) is excessive, realign the control unit following the procedure
outlined in paragraph 3-64j.
At constant ambient temperature, constant load, constant voltage and constant barometric pressure,
the set frequency should remain within a bandwidth of 1 percent of rated frequency for a period of 4
hours. If this bandwidth has been exceeded, realign the control unit in accordance with paragraph
3-64j.
If the preceding solutions to the specific problem do not resolve the problems, replace and repair the
control unit, actuator (paragraph 3-43) or load measuring unit (paragraph 3–63) as required.
c. Removal.
(1) Tag and disconnect electrical connectors to governor control unit.
(2) Remove nuts (1, figure 3-68), Iockwashers (2), nuts (3), Iockwashers (4) and bracket (5), threaded
rod (6) and lift governor control unit from mounting bracket.
3-158
ARMY TM 9-6115-464-34
AIR FORCE 35C2-3-445-2
NAVY NAVFAC P-8-624-34
