TM 10-4930-351-14
0013 00
CONTROL BOX
ELECTRICAL SYSTEM MALFUNCTIONS.
Pumping assembly electrical system malfunctions are problems related to the control box, interconnecting cables, alternator,
starter and pumping assembly sensors. Electrical troubleshooting of the pumping assembly is best accomplished by
continuity and voltage checks of the circuitry associated with a reported problem. A system schematic and a functional
description of the electrical system is provided in this section, as well as a system interconnecting drawing, as a
troubleshooting aid.
PUMPING ASSEMBLY PRINCIPLES OF OPERATION (Refer to System Electrical Schematic).
When the battery is initially connected to the system through the NATO connector (NATO CONN), 28 VDC is applied:
a. to the BATT input of VR1, the system voltage regulator.
b. across circuit breaker CB2 to the auxiliary pump module and the input side of INTAKE HEATER switch S2.
c. across circuit breaker CB1 to the input side of ENGINE START-RUN-STOP switch S3, shown in the STOP
position.
When ENGINE switch S3 is placed in the momentary START position, 28 vdc is applied from switch terminal 1 to the
starter solenoid, energizing the starter to crank the engine. At the same time, 28VDC is applied from the output side of the
starter solenoid to the pick up coil of FUEL SHUTOFF SOLENOID L1 on the engine, opening fuel ports to the engine fuel
injectors.
After the engine starts, the ENGINE switch is released to the RUN position. The starter solenoid is deenergized, power is
removed from the starter and FUEL SHUTOFF SOLENOID L1 pick up coil is deenergized. Simultaneously, the alternator
output is applied to the voltage regulator/rectifier where it is rectified to DC and regulated to 28 VDC. The regulator output
at terminal "/" is applied across the EMERGENCY STOP switch to provide electrical power to the system. The regulator
output is also applied through relay K1 to FUEL SHUTOFF SOLENOID L1 hold coil to hold the fuel ports open.
System power is available at the input of FAULT LIGHTS switch S5 any time the system is operating or the ENGINE
START-RUN-STOP switch is in the RUN position. In the BLACKOUT position, no power is applied to the panel lights or
the fault lights. When switch S5 is placed in the ON position, power is applied across dimmer control R1 to panel lights
CR1, CR2, CR3 and CR4. The illumination level is adjusted by operating dimmer control R1. All panel lights are Light
Emitting Diodes (LEDs) to assure low power operation and long life.
The four system fault lights are grouped in the center of the control panel. The ENGINE HOT, LOW OIL PRESSURE and
PUMPAGE HOT indicators illuminate red to warn the operator of a condition dangerous to personnel or the system. The
ALTNTR indicator illuminates yellow to caution the operator of an electrical malfunction which may limit or preclude
continued system operation. FAULT LIGHTS switch S5 must be ON for any of the fault lights to operate.
The LOW OIL PRESSURE fault light is controlled by a pressure sensor on the engine. If the oil pressure decreases to an
unsafe level during operation, the contacts in sensor S7 close, providing a current path from ground through the sensor, LED
CR6 and FAULT LIGHTS switch S5 to the 28 vdc line after EMERGENCY STOP switch S5.
0013 00-5
