TM 5-2420-230-24-1
(c)
If the resistance being measured is connected to a circuit, turn electrical master switch to OFF position
When measuring high resistance, be careful not to contact adjacent points, even if they are insulated,
to prevent damage to equipment.
(d)
Connect test leads to circuit being measured. Some insulators have a relatively low insulation resistance,
which can affect the resulting measurement.
(e)
Read resistance value on digital display.
(2)
Continuity checks.
(a)
Place the function/range switch in any Ohm range.
NOTE
Some meters show "1+m" (or simply "1") when function/range switch is in any Ohm position.
(b)
Connect red test lead to Volt-Ohm connector and black lead to COM input connector on meter. When the test
leads are separated or measuring an out-of-range resistance, the digital display will indicate OL (Over
Limit).
(c)
Put one test probe at one end of wire or circuit to be tested. Use other test lead to trace circuit. When
continuity is established, an Ohm symbol will appear in the upper-left corner of the digital display. If contact
in the wire is maintained long enough (about a 0.25 second), the OL will disappear and the resistance value
of the wire or circuit will appear next to the symbol.
(d)
If your multimeter does not work in this manner, learn how it operates before performing troubleshooting.
(3)
Voltage measurements. The IHMEE is equipped with 24-Vdc circuits. Troubleshooting procedures will reference
24-Vdc measurement, however, the value can vary. When the batteries are fully charged, 25.2-Vdc can be
measured on an open 24-Vdc circuit and 29-Vdc can be measured when the engine is running at 1,000 RPM.
(a)
Connect red test lead to Volt-Ohm input connector and black lead to COM input on meter. If a DC-AC
switch is present, ensure it is set to DC position.
(b)
Set function/range switch to desired volts position. If the magnitude of the voltage is not known, set the
switch to a range which will be able to read most voltages seen on vehicle (typically, a 200-Vdc range will
do). Then, reduce the range until a satisfactory reading is obtained.
c. General Wire Test Procedures. IHMEE troubleshooting isolates problems down to the components that could
cause a specific failure. When all of the components in a circuit are tested without isolating a fault, the wires are the
only other components that could be suspected of being damaged. Each wire that must be tested may pass through two
or more connectors. The following procedures provide general instructions for testing electrical wires. These
procedures will either attempt to measure a voltage at the working end of a circuit or continuity from the power end of a
specific wire to the working end. Before either of these tests are performed, all connectors in the circuit must be
checked for looseness.
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