Schematic Reference: Radio/Audio System Schematics

The length of the antenna coax cable lead-in and antenna body determines the total system ground measurement.

Important: Always zero out the DMM before taking a resistance measurement in order to ensure an accurate reading.

1. Disconnect the antenna lead-in connector from the radio receiver.
2. Measure the resistance from the negative battery post to the coax outer conductor connector.
3. The resistance measured should be as follows:

•	Cable less than 5 ft--No more than 0.035 ohms

•	Cable 5-13 ft--No more than 0.060 ohms

•	Cable 13-20 ft--No more than 0.085 ohms

4. Test the following when the resistance is greater than specified:

•	Base of the antenna for a poor connection to body ground.

•	The coaxial cable interconnects for a poor connection or corrosion.

•	Test for an open or high resistance from the battery negative cable to the body. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

•	Do not use black (phosphate-coated) hardware for antenna mounting purposes. This type of fastener is unreliable in making good connections.

5. After finding and correcting the condition, operate the system in order to verify the repair.

Perform the Antenna Checking Procedures after confirming the integrity of the antenna ground.

Perform the following tests for the type of antenna on the vehicle.

Using a Test Antenna

Use a test mast antenna to check for poor vehicle antenna operation. Unplug antenna lead-in connector from radio receiver and plug the test antenna into radio. Make sure the test antenna base is grounded to the vehicle chassis and keep hands off the mast. Check radio reception in an area away from electrical interferences. Tune to several weak and strong AM and FM stations. If the radio reception improved, the problem exists with the vehicle antenna and/or lead-in cable. If the reception is still poor, refer to Audio System Troubleshooting Hints .

Antenna Coaxial Cable Testing

Disconnect the antenna coax cable connector from the radio receiver and perform the following measurements.

Important: Always zero out the DMM before taking a resistance measurement in order to ensure an accurate reading.

1. Measure the total resistance from end to end of center conductor of the coax cable:

•	RG-58/RG-59 type cable--Less than 0.20 ohms

•	RG-62/RG-62M type cable--Less than 3.5 ohms

2. When checking the resistance, cautiously wiggle the lead-in tip and cable. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
3. Test for continuity between the center conductor of the coax cable (radio end) to the center connector of the antenna attachment point .
4. If there is no continuity between the center conductor of the coax cable (radio end) to the center connector of the antenna attachment point, replace the antenna base.
5. Measure the resistance from the cable center conductor to metal case. Reading should be infinite.
6. If equipped with a powered antenna, test for an open or short to ground on the radio on signal circuit.
7. Replace the antenna and/or lead-in cable when the above readings are not obtained.