ARMY TM 9-6115-670-14&P
2-3
Table 2-1. APU Control Unit Controls and Indicators
Key
Name
Type
Function
1
A-C VOLTS
AC voltmeter
Indicates APU output voltages; normal
output is 120 V line-to-neutral or 240 V line-
to-line.
2
PERCENT MOTOR
LOAD CURRENT
AC ammeter
Indicates APU output current in 5%
increments of APU rated output of 52.1
amps.
3
HERTZ
Frequency meter
Indicates APU output frequency in 0.2 Hz
(0.1 Hz – JTACS) increments; normal output
is 60 Hz.
4
HOUR
Hour meter
Indicates APU operating time in hours and
tenths of hours.
5
D-C AMPERES
DC ammeter
Indicates DC current flow to and from system
batteries in 1.0 amp increments; when
batteries are fully charged, indication is near
0. A high reading indicates low charge.
6
WATER
Dial indicator gauge
Indicates water temperature in degrees
fahrenheit (°F); normal operating temper-
ature is from 170°F to 200°F (93°C to 97°C).
7
ENGINE START/
PRE-HEAT
3-position spring-loaded
switch
Up position (ENGINE START) energizes
APU starter; middle position is normal
operating setting; down position (PRE-
HEAT) preheats engine glow plugs prior to
starting.
8
A.C. POWER
Toggle switch
In ON position, provides output power from
APU.
9
MASTER
Toggle switch
In ON position, supplies DC power to all
control circuits.
10 OVER-VOLTAGE
24 VDC light (red)
When lit, indicates over-voltage fault.
11 OVERSPEED
24 VDC light (red)
When lit, indicates engine over-speed fault.
12 LOW FUEL
24 VDC light (red)
When lit, indicates low fuel fault.
13 WATER TEMP
24 VDC light (red)
When lit, indicates engine high coolant
temperature fault.
14 OIL PRESSURE
24 VDC light (red)
When lit, indicates low engine oil pressure
fault.
15 BATTLE SHORT
Toggle switch
Permits emergency operation by bypassing
protective device circuits, except overload
circuit, and locks out starter circuit.
16 EMERGENCY
SHUTDOWN
Pushbutton switch
When depressed, interrupts battery voltage
to control circuits causing APU to shut down.
17 AC VOLTAGE
ADJUST
Rheostat
Allows adjustment of APU output voltage.
