Jeep Cherokee 2000 Service Manual - page 407
TEST 1
Test 1 determines if the antenna mast is insulated
from the base. Proceed as follows:
(1) Unplug the antenna coaxial cable connector
from the radio chassis and isolate.
(2) Connect one ohmmeter test lead to the tip of
the antenna mast. Connect the other test 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) 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 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 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.
(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 vehicle
fender. Connect the other test lead to the outer crimp
on the antenna coaxial cable connector.
(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.
RADIO FREQUENCY INTERFERENCE
WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS,
REFER
TO
GROUP
8M
-
PASSIVE
RESTRAINT SYSTEMS BEFORE ATTEMPTING ANY
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.
For complete circuit diagrams, see Group 8W -
Wiring Diagrams. Inspect the ground paths and con-
nections at the following locations:
•
Blower motor
•
Electric fuel pump
•
Engine-to-body ground strap
•
Generator
•
Ignition module
•
Radio antenna base ground
•
Radio receiver chassis ground wire or strap
•
Wiper motor.
If the source of RFI or EMI noise is identified as a
component on the vehicle (i.e., generator, blower
motor, etc.), the ground path for that component
should be checked. If excessive resistance is found in
any ground circuit, clean, tighten, or repair the
ground circuits or connections to ground as required
before considering any component replacement.
For service and inspection of secondary ignition
components, refer to the Diagnosis and Testing sec-
tion of Group 8D - Ignition Systems. Inspect the fol-
lowing secondary ignition system components:
•
Distributor cap and rotor
•
Ignition coil
•
Spark plugs
•
Spark plug wire routing and condition.
Reroute the spark plug wires or replace the faulty
components as required.
If the source of the RFI or EMI noise is identified
as two-way mobile radio or telephone equipment,
check the equipment installation for the following:
•
Power connections should be made directly to
the battery, and fused as closely to the battery as
possible.
•
The antenna should be mounted on the roof or
toward the rear of the vehicle. Remember that mag-
netic antenna mounts on the roof panel can adversely
affect the operation of an overhead console compass,
if the vehicle is so equipped.
•
The antenna cable should be fully shielded coax-
ial cable, should be as short as is practical, and
should be routed away from the factory-installed
vehicle wire harnesses whenever possible.
8F - 6
AUDIO SYSTEMS
XJ
DIAGNOSIS AND TESTING (Continued)