ARMY TM 9-6115-604-12
NAVY NAVFAC P-8-633-12
4-27.
MAINTENANCE OF OIL PRESSURE ALARM AND SHUTDOWN SWITCH OP1/OP2 . Oil pressure alarm and
shutdown switch OP1/OP2 (see figure 3-3) senses engine lubricating oil pressure. When lubricating oil pressure falls be-
low 39 ± 2 psi (269 ± 14 kPa), the normally closed contacts of switch OP2 trip the low oil pressure alarm. If pressure
continues to fall to 30 ± 2 psi (207 ± 14 kPa), switch OP1 will shut the set down.
a.
Remove.
(1)
Disconnect electrical connector from switch.
(2)
Remove switch from engine tee.
b.
Test.
(1)
Set multimeter to RX1 scale and connect across switch contacts B and C.
(2)
Connect switch to a source of pressurized lubricating oil or air. Pressurize to 50 psi (345 kPa).
Multimeter should read infinity.
(3)
Decrease pressure gradually When pressure has fallen to 39 ± 2 psi (269 ± 14 kPa), the switch
should open. Multimeter should read zero
(4)
Connect the multimeter across switch contacts A and D.
(5)
Decrease pressure gradually. When pressure has fallen to 30 ± 2 psi (207 ± 14 kpa), the switch
should close. Multimeter should read zero ohms.
c.
Install. See Figure 3-3.
(1)
Install switch on tee.
(2)
Install electrical connections to switch.
(3)
Run the engine and check for leakage around switch, tighten as necessary.
4-28.
MAINTENANCE OF SPEED SWITCH SS1/SS2/SS3. The speed switch SS1, SS2, and SS3 is in one cylindrical
housing and mounted on the tachometer drive of the engine fuel pump. The switch functions to disconnect the starters
(SS1), arm the under frequency and under voltage circuits (SS2), and to shut down the engine upon an overspeed
condition (SS3).
a.
Remove. Refer to Figure 1-8.
(1)
Disconnect electrical connector J1 from the speed switch.
(2)
Loosen neoprene coupling and remove switch.
b.
Test.
(1)
Connect the speed switch to a variable speed motor equipped with a tachometer.
(2)
Drive the speed switch at rotational speeds between 0 and 1134 rpm. Using a multimeter check
performance of SS1/SS2/SS3 against data given in Figure 4-28.
(3)
Run RPM to 1200 to ensure it trips and resets properly.
(4)
The switch is adjustable but not repairable If it can not be adjusted to operate within the above limits,
replace the switch.
c.
Adjust . See Figure 4-28.
(1)
Remove cover screw for switch to be adjusted.
(2)
Insert 1/16 inch (1 59 mm) Allen wrench into adjusting screw.
CAUTION
Too many counterclockwise turns will remove setscrew from locknut assembly.
(3)
Turn clockwise to Increase trip point; counterclockwise to decrease trip point.
(4)
Test in accordance with step b, above.
(5)
Replace cover.
4-79
