572 8 DIAGNOSTIC TOOLS AND ACCESSORIES
Jumper Wires
Figure 552 Jumper wires
Jumper wires allow a circuit to by-pass a suspected
opening or break in a circuit. Use a jumper wire
to check for open relay contacts, wire breaks and
poor ground connections. Several jumper wires with
different tips should be available.
Figure 553 Troubleshooting w ith jumper wires
If the circuit works correctly with the jumper wire in
place, but does not work when the jumper w ire 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 no t illum inate.
• Jumping the switch does not illumina te the lig ht.
• 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?
EGES-270-1
Read all safety instructions in the "Safety Information" section of this manual before doing any procedures.
Follow all warnings, cautions, and notes.
© August 2008 Navistar, Inc.
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