TM 9-6115-664-13&P
1-15. ENGINE PREHEATING.
If ambient temperature drops below 32º F, the engine PREHEAT switch (A1-S2) should be activated before the
engine is cranked. Placing the PREHEAT switch in the OIL (up) position energizes relay A2-K3, providing power to the oil
glow plug located in the oil reservoir of the engine. Placing the PREHEAT switch in the AIR (down) position energizes
relay A2-K4, providing power to two air glow plugs located in the engine intake manifold. The PREHEAT switch is spring
loaded and will return to the off position when released.
1-16. EMERGENCY STOP SWITCH.
When the remote control panel EMERGENCY STOP switch (A4-S3) is pushed in, it removes 28 VDC power from
the fuel solenoid and causes the engine to stop. While the EMERGENCY STOP switch is activated, power is removed
from the starter solenoid and the engine cannot be cranked. The switch must be pulled out to the off position before the
engine can be started again and circuitry functions return to normal.
1-17. MALFUNCTION INDICATORS.
a.
If the engine exceeds normal operating temperature, a heat sensitive, high cylinder head temperature switch
(HT) closes. The circuitry removes ground from relay A1-K2, causing power to be removed from the fuel solenoid hold
coil. A red HIGH ENGINE TEMPERATURE LED (A4-LED 4, located on the remote control panel) illuminates.
b.
If engine oil pressure drops below a safe operating level, a low oil pressure switch (OP) opens. The circuitry
removes ground from relay A1-K2, causing power to be removed from the fuel solenoid hold coil. A red LOW OIL
PRESSURE LED (A4-LED 3, located on the remote control panel) illuminates.
1-18. REMOTE OPERATION.
a.
The APU may be operated using a remote control panel supplied with the system. The operator places both
START / PRIME RUN / OFF switches (local and remote control panels) in the OFF position. The REMOTE / LOCAL
switch (A1-S1, located on the local control panel) is moved to the REMOTE position. The control of the APU is switched
to the remote control panel. Electrical operation of the APU is the same whether controlled from the local or remote
control panels. The remote control panel is equipped with a PRESS TO TEST LAMPS switch (A4-S6). When the switch
is depressed, all LEDs shall illuminate, verifying that they are functioning properly.
b.
The BATTLE SHORT switch (A4-S5, located on the remote control panel) overrides the shutdown systems of
the APU (high engine temperature, low oil pressure). Placing the switch in the ON position sends a 28 VDC signal to the
local control panel and energizes relay A1-K2, preventing engine shutdown in low oil or high temperature conditions.
1-19. FUEL SYSTEM.
a.
The APU fuel system (Figure 1-6) is designed to interface with the vehicle and operate on the same fuels as the
vehicle. The system is self venting and requires no fuel return line to the vehicle. The APU may be operated from an
auxiliary fuel source up to twenty-five feet away using the auxiliary fuel line provided.
1-17
