until all sources of power connected to the circuit or
until all sources f power connected to the circuit or
device to be tested are disconnected.
The
device to be tested are disconnected.
The
multimeter will be damaged if this procedure is not
muitimeter will be damaged if this procedure is not
followed.
followed.
d. Separate the ends of the test leads and clip the
3-52. Troubleshooting Electrical Harnesses and
leads across the portion of the circuit or component
Cables. The following method should be used to
being tested. (Either one of the two colored leads may
determine if a malfunction exists in a harness or cable:
be clipped to the test points.)
a. Visually inspect harness or cable for breaks
e. Read the ohms on the black area at the top of
cuts or other damage that could cause a "short" or
the scale.
"open" circuit.
Note. For range R x 1, read the fur directly; for
b. Disconnect both ends of the harness or
range R x 100, multiply the reading indicted by 100
cable containing the circuit.
c. Connect a jumper lead between the circuit
or add two zeros I, the reading; for range R x 10,000,
socket or pin contact and a common ground (hull, turret,
multiply the reading indicated by 10,000 or add four
etc.).
zero to the reading.
d. Attach the "ground" (negative) led of the
Example: A 20,000-ohm resistance should be
multimeter to the common ground.
checked on the R x 100 range scale. The reading on
e. Present multimeter for continuity test.
the scale will be 200. Adding two zero will give 20,000
f.
Check circuit for continuity by touching
ohms.
socket or pin contact in opposite end of harness or cable
3-50. Infinite and Zero Multimeter Readings .
with meter (positive) lad test probe.
a. Infinite reading. An infinite reading is open
g. Full-sale deflection of needle indicates a
circuit (direct-current) reading.
There will be no
complete circuit. An intermittent or no needle deflection
movement of the multimeter pointer when an open
indicates an "open" circuit.
circuit exists. Infinite position on the ohmmeter range
h. Install new harness or cable if circuit is
scale is marked with the symbol oo .
"open" (broken).
b. Zero reading.
A zero reading indicates a
continuous circuit with too small resistance to be
Note. Harness or cables may be repaired if
measured with multimeter.
damage is light.
3-51. Resistance Readings. A resistance reading is
taken to determine either the electrical condition of a
Caution: Set range selector on R x I scale and
resistance of the component or circuit is known, a
voltage (V) selector switch on "0' for all continuity
resistance test will indicate, after interpretation of the
tests on wiring harnesses and cables.
Range
readings, the fault in the circuit. Resistance readings of
selector switch must be set on 50 V for all voltage
components in the equipment are nominal only and may
tests of wiring harnesses and cables unless
vary slightly from equipment to equipment and also
otherwise specified .
depend upon the accuracy and condition of the
multimeter being used to perform the required test.
Section V. HEADLIGHT ASSEMBLIES
on the front of the hull; each is protected by a brush
3-53. General.
guard. The headlight assemblies are elevated above
3-54. This section contains instruction for removal and
the
installation of the headlight assemblies.
3-55. Description and Data.
3-56. Description. Two headlight clusters remounted
3-29