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572
Jumper Wires
Figure 552 Jumper wires
Jumper wires allow a circuit to by-pass a suspected
opening or break in a circuit.
to check for open relay contacts, wire breaks and
poor ground connections. Several jumper wires with
different tips should be available.
Read all safety instructions in the "Safety Information" section of this manual before doing any procedures.
8 DIAGNOSTIC TOOLS AND ACCESSORIES
Use a jumper wire
EGES-270-1
Follow all warnings, cautions, and notes.
© August 2008 Navistar, Inc.
Figure 553 Troubleshooting with jumper wires
If the circuit works correctly with the jumper wire in
place, but does not work when the jumper wire is
removed, the circuit is open.
A circuit with no openings or breaks has continuity
(uninterrupted current flow) and needs no further
testing.
An opening in the ground circuit exists for the
following:
•
A switch is closed but the light does not illuminate.
•
Jumping the switch does not illuminate the light.
•
Jumping the light to the ground causes the light to
illuminate.
Voltmeter
Use a voltmeter to answer the following questions:
•
Does the circuit have voltage?
•
What is the voltage reading?
•
What is the voltage drop across a load device?
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