Jeep Wrangler 1997 Manual page 329

TJ
DIAGNOSIS AND TESTING (Continued)
ANTENNA
WARNING : ON VEHICLES EQUIPPED WITH AIR-
BAGS, REFER TO GROUP 8M - PASSIVE
RESTRAINT SYSTEMS BEFORE ATTEMPTING
STEERING WHEEL, STEERING COLUMN, OR
INSTRUMENT PANEL COMPONENT DIAGNOSIS OR
SERVICE . FAILURE TO TAKE THE PROPER PRE-
CAUTIONS COULD RESULT IN ACCIDENTAL AIR-
BAG DEPLOYMENT AND POSSIBLE PERSONAL
INJURY
The following four tests are used to diagnose the
antenna with an ohmmeter :
" Test 1 - Mast to ground test
" Test 2 - Tip-of-mast to tip-of-conductor test
" Test 3 - Body ground to battery ground test
" Test 4 - Body ground to coaxial shield test.
The ohmmeter test lead connections for each test
are shown in Antenna Tests (Fig. 1).
NOTE : This model has a two-piece antenna cable.
Tests 2 and 4 must be conducted in two steps to
isolate a coaxial cable problem ; from the coaxial
cable connection under the right end of the instru-
ment panel near the right cowl side panel to the
antenna base, and then from the coaxial cable con-
nection to the radio chassis connection .
Fig. 1 Antenna Tests
J898F-7
TEST 1
Test 1 determines if the antenna mast is insulated
from the base . Proceed as follows :
(1) Disconnect the antenna cable lead from the
radio chassis and isolate .
AUDIO SYSTEMS 8F - 5
(2)
Connect one ohmmeter lead to the tip of the
antenna mast and the other lead to the antenna
base. Check for continuity.
(3) There should be no continuity. If continuity is
found, replace the faulty or damaged antenna base
and cable assembly.
TEST 2
Test 2 checks the antenna for an open circuit as
follows :
(1) Disconnect the antenna cable lead from the
radio chassis .
(2) Connect one ohmmeter test lead to the tip of
the antenna mast. Connect the remaining lead to the
tip of the antenna cable lead (the part inserted into
the radio).
(3) Continuity should exist (the ohmmeter should
only register a fraction of an ohm). High or infinite
resistance indicates damage to the base and cable
assembly . Replace the faulty base and cable, if
required .
TEST 3
Test 3 checks the condition of the vehicle body
ground connection . This test should be performed
with the battery positive cable removed from the bat-
tery. Disconnect both battery cables, the negative
cable first. Reconnect the negative cable and perform
the test as follows :
(1) Connect one ohmmeter test lead to the vehicle
fender and the other lead to the battery negative
post.
(2) The resistance should be less than one ohm .
(3) If the resistance is more than one ohm, check
the braided ground strap connected to the engine and
the vehicle body for being loose, corroded, or dam-
aged. Repair the ground strap connection, if required .
TEST 4
Test 4 checks the condition of the ground between
the antenna base and the vehicle body as follows :
(1) Connect one ohmmeter test lead to the fender
and the other lead to the crimp on the coaxial
antenna cable shield.
(2) The resistance should be less then one ohm .
(3) If the resistance is more then one ohm, clean
and/or tighten the antenna base to fender mounting
hardware .