Jeep 1996 Grand Cherokee Service Manual page 471

8W - 01 - 6
DIAGNOSIS AND TESTING (Continued)
TROUBLESHOOTING TESTS
Before beginning any tests on a vehicles electrical
system use the Wiring Diagrams and study the cir-
cuit. Also refer to the Troubleshooting Wiring Prob-
lems section in this section.
TESTING FOR VOLTAGE
(1) Connect the ground lead of a voltmeter to a
known good ground (Fig. 8).
(2) Connect the other lead of the voltmeter to the
selected test point. The vehicle ignition may need to
be turned ON to check voltage. Refer to the appropri-
ate test procedure.
Fig. 8 Testing for Voltage
TESTING FOR CONTINUITY
(1) Remove the fuse for the circuit being checked
or, disconnect the battery.
(2) Connect one lead of the ohmmeter to one side
of the circuit being tested (Fig. 9).
(3) Connect the other lead to the other end of the
circuit being tested. Low or no resistance means good
continuity.
TESTING FOR A SHORT TO GROUND
(1) Remove the fuse and disconnect all items
involved with the fuse.
(2) Connect a test light or a voltmeter across the
terminals of the fuse.
(3) Starting at the fuse block, wiggle the wiring
harness about six to eight inches apart and watch
the voltmeter/test lamp.
(4) If the voltmeter registers voltage or the test
lamp glows, there is a short to ground in that gen-
eral area of the wiring harness.
8W - 01 GENERAL INFORMATION
TESTING FOR A SHORT TO GROUND ON
FUSES POWERING SEVERAL LOADS
(1) Refer to the wiring diagrams and disconnect or
isolate all items on the fused circuit.
(2) Replace the blown fuse.
(3) Supply power to the fuse by turning ON the
ignition switch or re-connecting the battery.
(4) Start connecting the items in the fuse circuit
one at a time. When the fuse blows the circuit with
the short to ground has been isolated.
TESTING FOR A VOLTAGE DROP
(1) Connect the positive lead of the voltmeter to
the side of the circuit closest to the battery (Fig. 10).
(2) Connect the other lead of the voltmeter to the
other side of the switch or component.
(3) Operate the item.
(4) The voltmeter will show the difference in volt-
age between the two points.
TROUBLESHOOTING WIRING PROBLEMS
When troubleshooting wiring problems there are
six steps which can aid in the procedure. The steps
are listed and explained below. Always check for non-
factory items added to the vehicle before doing any
diagnosis. If the vehicle is equipped with these items,
disconnect them to verify these add-on items are not
the cause of the problem.
(1) Verify the problem.
(2) Verify any related symptoms. Do this by per-
forming operational checks on components that are
in the same circuit. Refer to the wiring diagrams.
Fig. 9 Testing for Continuity
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