SECTION 7 - GENERAL ELECTRICAL INFORMATION & SCHEMATICS
7-4
3121784
Continuity Measurement Over Long Distances
When trying to determine continuity of a harness or
wire, longer than the reach of standard instrument
leads, is possible to perform the check without exces-
sively long leads. Using the other wires in the harness
one can determine the condition of a particular wire in
the harness.
Requirements:
• Harness with at least three separate wires including
the wire under test.
• These wires must be able to be isolated from other
wires, etc.
• Jumper or method to connect contacts on one side
of harness.
• Meter that can measure resistance or continuity.
Procedure
Test multimeter leads resistance. Subtract this value
from the measured resistance of the wires to get a more
accurate measurement.
Consult the circuit schematic to determine which wires
to use in addition to wire under test, here called wire #1
and wire #2, and how to isolate these wires. These wires
should appear in the same connectors as the wire under
test or are within reach of the jumper.
1. Disconnect all connections associated with the wire
under test and the two additional wires. If harness is
not completely isolated disconnect battery terminals
also, as a precaution.
2. Measure continuity between all three wires, the wire
under test, wire #1 and wire #2. These should be
open. If not, repair the shorted wires or replace the
harness.
3. On one side, jumper from contact of wire #1 and wire
#2.
4. Measure continuity between wire #1 and wire #2. If
there is continuity, both wires are good and can be
used for this test. If there is not continuity, either wire
could be bad. Check connections and measurement
setup. Redo measurement. If still no continuity, repair
wires or consult schematic for other wires to use for
test.
5. Jumper from wire under test to wire #1.
6. Measure continuity. If there is continuity, the wire
under test is good. Resistance of a wire increases as
the length increases and as the diameter decreases.
One can find the continuity of two wires, here #1 and #2,
at once by following steps 1 through 4. If there is a prob-
lem the third wire is used to troubleshoot the other
wires. To find the problem, start at step 1 and use the
entire procedure.
7.3
ELECTRICAL SCHEMATICS MANUALS
The electrical schematics manuals are separate from this
manual. They are available online (Online Express or
www.jlg.com - Manuals) in the same folder where this
Service Manual was found.
Go to
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