Antenna, Radio: Testing and Inspection

WARNING: DISABLE THE AIRBAG SYSTEM BEFORE ATTEMPTING ANY STEERING WHEEL, STEERING COLUMN, SEAT BELT TENSIONER, SIDE AIRBAG, OR INSTRUMENT PANEL COMPONENT DIAGNOSIS OR SERVICE. DISCONNECT AND ISOLATE THE BATTERY NEGATIVE (GROUND) CABLE, THEN WAIT TWO MINUTES FOR THE AIRBAG SYSTEM CAPACITOR TO DISCHARGE BEFORE PERFORMING FURTHER DIAGNOSIS OR SERVICE. THIS IS THE ONLY SURE WAY TO DISABLE THE AIRBAG SYSTEM. FAILURE TO TAKE THE PROPER PRECAUTIONS COULD RESULT IN ACCIDENTAL AIRBAG 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.

Fig.1 Antenna Test:

The ohmmeter test lead connections for each test are shown in Antenna Tests.

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 outboard side of the glove box opening 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:
1. Disconnect the antenna coaxial cable connector from the radio receiver chassis and isolate. Remove the antenna mast from the antenna base.
2. Insert one ohmmeter test lead into the socket for the antenna mast in the center of the antenna base. Connect the other test lead to the perimeter of 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 coaxial cable connector from the radio receiver chassis.
2. Connect one ohmmeter test lead to the antenna mast in the center of the antenna base. 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 battery. 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 terminal post.
2. The resistance should be less than one ohm.
3. If the resistance is more than one ohm, check the braided ground strap(s) connected to the engine and the vehicle body for being loose, corroded, or damaged. Repair the ground strap connections, 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.