TM 55-1930-203-10
2-27. Instruments and Warning Lights
a. General. Instruments and warning lights used by the operator of the LARC are located in the cab in front of and to either side of
the operator. In addition, one set of machinery temperature and pressure gages (fig. 2-11) are located on each side of the cargo
space bulkhead at the coaming. The set on the port side indicates temperatures and oil pressures of the port machinery. The set on
the starboard side indicates temperatures and oil pressures of the starboard machinery.
b. Instruments and Warning Lights Located in Cab.
(1) Tachometer. The tachometer (3 and 5, sheet 1, fig. 2-1) indicates the engine speed in revolutions per minute. Each
tachometer is equipped with two indicating needles, one for each engine to which it is connected. Two tachorneters are supplied on
the LARC: one connected to the two port side engines, the other to the two starboard side engines. Engine idling r.p.m. is 550 and
maximum r.p.m. without load is 2120. The engines are governed at 2100 r.p.m.
(2) High beam indicator light. The high beam indicator light (6, sheet 1) is connected in parallel with the headlight dimmer
switch and illuminates when the headlights are switch to high beam.
(3) Warning lights. The warning lights, mounted on the cab port and starboard bulkheads, consist of individual lamps grouped
together. The port warning lights (32, sheet 4) contain lamps for the port machinery and low hydraulic oil level. The starboard
warning lights (16, sheet 1) contain lamps for the starboard machinery. One or more lamps will illuminate if any of the following
conditions occur:
(a) Low converter oil pressure.
(b) High transmission oil temperature.
(c) High engine water temperature.
(d) Low engine oil pressure.
(e) High gathering box oil temperature.
(f) Low gathering box oil pressure. (This warning light is no longer used; it was originally connected on LARC's 5 through
18.)
(g) Low marine gear oil temperature.
(h) High marine gear oil temperature.
(i) Low level hydraulic oil.
(4) Battery-generator indicator. The battery-generator indicator (13, sheet 1) indicates the battery charge condition. Normal
indicator reading is in the green zone. The indicator may indicate high charging rate for the first few minutes after the engines have
started and before the generators have restored the depleted current to the batteries. High charging rate for an extended period may
indicate a weak battery, faulty generator or regulator, or a short circuit. If any one of these conditions occur, report promptly to
organizational maintenance.
(5) Marine gear oil pressure gage. During marine operations, the marine gear oil pressure gage (14, sheet 1) indicates the oil
pressure of the marine gear. Normal indication on this gage is 180 to 210 p.s.i. Indication of less than 200 p.s.i. at 1800 r.p.m.
engine speed should be reported to organizational maintenance.
NOTE
When shifting from ahead to astern or from astern to ahead, the marine gear oil pressure will drop to zero, and then be restored.
(6) Master warning light. The master warning light (20, sheet 2) will illuminate when any of the warning lights mounted on the
cab port or starboard bulkheads illuminate. The purpose of the master warning light is to direct the operator's attention to the warning
light panels.
(7) Steering pressure gage. The steering pressure gage (21, sheet 2) is used only by organizational maintenance personnel
when aligning the wheels. These gages should read zero at aU times when operating the LARC. If other indication is observed,
report to organizational maintenance.
(8) Main air pressure gage. The main air pressure gage (23, sheet 2) indicates the air pressure available in the main air
system. The reading on this gage should not exceed 155 p.s.i.
(9) Tire air gage. The tire air gage (24, sheet 2) indicates the air pressure in the tire inflation system, including the air in the
tires.
c. Instruments Located on Gage Boards.
(1) Engine oil pressure gage(l, 6, fig. 2-11). This gage indicates the pressure of the engine oil. When the engine is operating
at low idle range, the nornal indication is 5 to 12 p.s.i. at 550 r.p.m.; high idle range is 30 to 50 p.s,.i. at 1200 r.p.m.; drive range is
40 to 60 p.s.i. at 1750 r.p.m. The engine oil pressure gage minimum indication is 18 p.s.i. at 12 r.p.m., 28 p.s.i. at 1800 r.p.m., and
30 p.s.i. at 2000 r.p.m. If the oil pressure indications are not within the above ranges, report to organizational maintenance.
(2) Transmission oil pressure gage (2, 5). This gage indicates the oil pressure in the transmission LUBE oil system. The
normal gage indication is 140 to 160 p.s.i. Report readings greater or less than that amount to organizational maintenance.
(3) Gathering box oil pressure gage (3). This gage indicates the oil pressure in the
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