Jeep 1997 Grand Cherokee Service Manual page 444

8F - 8 AUDIO SYSTEMS
DIAGNOSIS AND TESTING (Continued)
wire harness connectors for continuity to ground. In
each case there should be no continuity. If OK, go to
Step 13. If not OK, repair the short circuit as
required.
(13) For each inoperative speaker location, check
the resistance between the amplified feed (+) circuit
and the amplified return (-) circuit cavities of the
amplifier wire harness connectors. The meter should
read between 3 and 8 ohms (speaker resistance). If
OK, replace the faulty amplifier. If not OK, go to
Step 14.
(14) Unplug the speaker wire harness connector at
the inoperative speaker.
between the amplified feed (+) circuit cavities of the
speaker wire harness connector and the amplifier
wire harness connector. Repeat the check between
the amplified return (-) circuit cavities of the speaker
wire harness connector and the amplifier wire har-
ness connector. In each case there should be continu-
ity. If OK, replace the faulty speaker. If not OK,
repair the open circuit as required.
ANTENNA
NO OR POOR RADIO RECEPTION
WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS, REFER TO
RESTRAINT SYSTEMS BEFORE ATTEMPTING ANY
STEERING WHEEL,
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 coaxial
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
instrument panel near the right cowl side panel to
the antenna base, and then from the coaxial cable
connection to the radio chassis connection.
TEST 1
Test 1 determines if the antenna mast is insulated
from the base. Proceed as follows:
Check for continuity
GROUP 8M - PASSIVE
STEERING COLUMN,
(1) Unplug the antenna coaxial cable connector
from the radio chassis and isolate.
(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 fixed antenna
OR
base and cable assembly or power antenna unit.
TEST 2
Test 2 checks the antenna for an open circuit as
follows:
(1) Unplug the antenna coaxial cable connector
from the radio chassis.
(2) Connect one ohmmeter test lead to the tip of
the antenna mast. Connect the other test lead to the
center pin of the antenna coaxial cable connector.
(3) Continuity should exist (the ohmmeter should
only register a fraction of an ohm). High or infinite
resistance indicates damage to the fixed antenna
base and cable assembly or the power antenna unit.
Replace the faulty antenna unit, 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 battery negative cable and
perform the test as follows:
(1) Connect one ohmmeter test lead to the vehicle
fender. Connect the other test lead to the battery
negative post.
(2) The resistance should be less than one ohm.
Fig. 1 Antenna Tests
ZG