C4, TM 9-2350-230-12
TABLE 8-5. OHMMETER METHOD OF ELECTRICAL TROUBLESHOOTING - CONTINUED
e. Test Point Designation. Ohmmeter test points are
CAUTION Never attempt to make ohmmeter tests
tabulated for each electrical circuit and referenced to an
until all sources of power connected to equipment to
accompanying illustration. The letter "P" denotes
be tested are disconnected. The ohmmeter will be
testpoint (terminal, plug, or receptacle) and is followed by
damaged if this procedure is not followed.
a number designating the test point numerical
sequence.
Multi-plug and receptacle designation are
also followed by a letter to indicate the specific pin or
ohmmeter on end points of circuit to be tested, or to two
socket. P1-A then will denote test point "1," pin "A."
terminals at which ends of component to be tested
Ground (gnd) means any part of vehicle that has a good
terminate. If a normal reading is obtained, circuit has no
electrical connection with the unit being tested. Electrical
breaks or openings.
circuits and tables are as follows:
Figure 8-3. Troubleshooting Master Relay and Battery
c. Resistance Reading. A resistance reading is taken
Power Circuits
to determine electrical condition of a coil, resistor,
Figure 8-4. Troubleshooting Generator and Voltage
capacitor, or complete circuit. When correct resistance of
Regulator Circuits
a unit is known, a resistance test will indicate if there is a
Figure 8-5.
Troubleshooting Engine Starter Circuit
fault in circuit.
Figure 8-6.
Troubleshooting Flame Heater Circuits
Figure 8-7.
Troubleshooting Indicator Panel Circuits
d. Infinity and Zero Ohmmeter Readings.
Figure 8-8.
Troubleshooting Fuel
Level Indicator
Circuits
(1) Infinity reading. An. infinity reading indicates that
Figure 8-9.
Troubleshooting Driver's Periscope Wiper
no path exists for current flow in a component, or that an
Circuits
open circuit exists. The ohmmeter indicator does not
Figure 8-10. Troubleshooting Bilge Pump Circuits
move when infinite resistance exists but remains at a
Figure 8-11. Troubleshooting
Personnel
Heater
point on ohmmeter scale usually marked by symbol "oo"
Circuits
or abbreviation INF" An ohmmeter should always give an
Figure 8-12. Troubleshooting Power Plant Indicator
infinity reading when test leads are disconnected.
and Warning Light Circuits
Figure 8-13. Troubleshooting Vehicle Driving Light
(2) Zero reading. A zero ohmmeter reading indicates
Circuits.
closed circuit with no measurable resistance. When a
known resistance is specified and a zero reading is
obtained, a short circuit exists within component or circuit
being tested. An ohmmeter should always be adjusted to
give a zero reading when test prods or clips are touched
together.
8-46