p. Fill hydraulic system with hydraulic oil MIL-
slotted adjustment control screw (34) to obtain a
pressure of 320 ± 10 psi.
q. Start the engine. (Refer to Operator and
Organizational Maintenance Manual).
s. Replace hex cap, shut down engine, drain hy
draulic system, remove pressure gauge, connect
Remove the hex cap (11, fig. 14-5) and washer
hydraulic output line to pump, and refill system with
(12) located on top of the pump housing, and adjust the
hydraulic oil, MIL-H-5606.
Section IV. SPEED SWITCH, TACHOMETER DRIVE AND ADAPTER
a. The speed switch, driven by the camshaft
through a tachometer drive assembly and an angle
adapter, provides sequenced control of circuits during
engine startup and protection against engine overspeed
during operation. Three sets of contact elements, S91,
S9-2, and S93, contained in the speed switch, are set
to open, close, or transfer by centrifugal force at certain
engine speeds. The speed switch drive gear is designed
to drive the speed switch at onehalf engine speed
b. At an engine speed of 580 to 620 rpm (acceler-
ating) element S91 transfers two sets of contacts,
energizing the field flash circuit and de-energizing the
crank relay to stop the starting motor.
On Class 1 sets, when the engine reaches the
speed range of 1180 to 1220 rpm (Mode I); 1650 to 1700
rpm (Mode H) element S92 closes, energizing the
electro-hydraulic governor which takes over control of
d. Speed switch element S9-3 consists of two sets
of contacts which are set to transfer at an engine speed
of 2425 ± 25 rpm to shut down the engine and prevent
damage to the equipment. Shutdown is achieved by
de-energizing the stop-run relay and the fuel solenoid,
cutting off fuel to the engine.
Elements S91 and S92 reset at 100 rpm (de-
creasing) below actuation speed. Element S93 is
manually reset by a pushbutton on the speed switch
1418. Speed Switch Removal.
Refer to Operator and Organizational Maintenance
Manual for removal of the speed switch.
14-19. Speed Switch Tests, Adjustment, Repair and
a. Connect a variable speed drive device to the
speed switch drive. The drive device must have a
tachometer in order to determine the speed of the device
b. With an ohmmeter on the R1 scale, reading
from the speed switch connector, check for the contact
conditions of elements S91, S9-2, and S9-3 illustrated
in figure 14-6.
c. When contact conditions are verified, as shown
in figure 14-6, start variable drive and gradually
increase speed, with ohmmeter connected to pins B and
A. At a speed of 300 ± 15 rpm, the ohmmeter should
indicate that contact AB opens. Hold the variable
speed drive at that speed and transfer the ohmmeter
leads to pins A and C. The ohmmeter should indicate a
d. Leave the ohmmeter leads connected to pins A
and C and gradually reduce speed. In the range of 190
to 210 rpm, the contacts of element S91 should reset to
the condition illustrated in figure 146. To verify
operation of element S9-1 contacts A and C, increase
drive speed gradually and observe that the contacts
close at 300 ± 15 rpm range.
e. Connect ohmmeter leads across pins D and E
and verify an open circuit. Increase drive speed and
observe that element S92 (contacts D and E) closes in
the speed range of 600 ± 20 rpm (Mode I); 840 ± 20 rpm
(Mode II). Gradually reduce speed to 490 minimum rpm
(Mode I); 725 minimum rpm (Mode II). Observe that
element S92 resets to the condition shown in figure
(Required for P/N 70-1105-3 and P/N 70-
1105-4 switches only) In order to bench
check the trip speeds, apply +24VDC to
terminals E and G of the MS3102R18-1P
connector with the case negative.
f. Connect ohmmeter across pins H and G and
verify a closed circuit. Increase drive speed gradually.
The contacts should open at a speed of 1200 to 1250
rpm. Hold drive speed and read contacts F and J.
Meter should indicate a closed circuit. Reduce drive
speed to less than 1000 rpm, press the manual reset
switch and observe with the meter that element S93
contacts reset to the condition shown in figure 146.
g. To obtain the required performance character
istics during tests c through f adjustments can be made.
By loosening screws (1, figure 14-7) and rotating the
cap and cover assembly relative to the body assembly,
the trip points of all three elements can be raised or
lowered. In addition, the trip speed of each individual
element can be raised or lowered by removing cover
screws as shown in figure 14-6 and turning appropriate
set screw located beneath cover screws with a 1/16 inch
Change 11 14-9