(5) Check for evidence of wear, binding,
assembly (5, fig. 3-11) in the box touches the down stop
damage, and bending of parts that might impair
screw (191 when the accelerator bearing is within 1/ inch
of the toe plate (or fixture).
(4) With the pedal depressed fully, adjust the
potentiometer for an ohmmeter reading of 30 to 50
(1) Disassemble accelerator pedal and linkage
ohms. Tighten the set screw (13) in the actuator to
according to figure 3-10.
securely engage the potentiometer shaft.
(2) Disassemble speed control box assembly
(5) With the pedal in the up position, a reading
according to figure 3-11.
of 15, 000 to 16, 000 ohms should be obtained on the
(1) Reassemble speed control box assembly
(6) Adjust position of microswitch (11) so its
according to the reverse of figure 3-11 and as follows:
(a) Install the microswitch (11) with the
plunger operates when the pedal is l/4 inch from the full
common terminal toward the rear of the box.
(7) Recheck the readings of steps 4 and 5 and
(b) Install the potentiometer (14) with the
the microswitch operation of step 6.
terminals toward the bottom of the box.
P1erform the inching control
(c) Connect the purple wire of the harness
adjustment this time.
(37) to the center terminal of the potentiometer. Connect
the yellow wire to the terminal nearest you.
(8) Disconnect ohmmeter and reconnect wires
(2) Reassemble the accelerator pedal and
linkage according to the reverse of figure 3-10.
(9) Remove the toe plate fixture and install the toe
To aid in adjustment it is
plate (TM 10-3930-620-12).
recommended that a toe plate fixture be substituted in
(10) Install the box cover (3) and gasket (4) using
place of the toe plate. The fixture should be the same
the two screws (1) and lock washers (2 .
thickness as the toe plate and large enough so the
3-7. Control Unit
accelerator rod bearing (13, fig. 3-10) will make contact
a. Voltage Test. This test should be made a with a
with it. Secure the fixture to the right hand mountings on
fully charged battery.
Set the voltmeter to the
the truck frame.
appropriate scale for each test. Connect the voltmeter
(1) Disconnect wires from speed potentiometer
negative and positive leads according to the - and +
(14. fig. 3-11 ). Connect ohmmeter between center
indicators given for each measurement. (fig. 3-12.)
terminal and terminal nearest you.
Note. 'The seat must be depressed and
(2) Loosen the set screw (13) in the actuator
emergency stop switch released when
arm 116) so the potentiometer shaft is free. .
performing these tests.
(3) Depress the accelerator pedal. Adjust the
yoke positions on the yoke rod (5, fig. 3-10) so the arm