Radio - Poor AM Reception
Article No.93-2-5
01/18/93
RADIO - POOR AM RECEPTION CAUSED BY POOR ANTENNA CONNECTIONS
FORD:
1990 CROWN VICTORIA
LINCOLN-MERCURY:
1990 GRAND MARQUIS
LIGHT TRUCK:
1989-90 BRONCO II
1989-92 RANGER
1991-92 EXPLORER
ISSUE:
Poor AM radio reception, such as fading or static, may be caused by poor antenna connections.
ACTION:
Perform the following diagnostic and repair procedures. If necessary, replace the antenna and antenna cable as required.
VERIFICATION
In some cases, a customer's concern may be caused by normal radio operating conditions. This is especially true if the customer complains of static in certain locations or while tuned to certain stations.
Obtain as much information from the customer as possible regarding the audio system's performance. The following descriptions will then help the technician and the customer decide whether the radio system concerns are caused by a defective audio system or are the results of normal operating conditions.
FADING
AM fade will occur under viaducts and in urban areas with tall buildings. Certain AM stations may lower their power in the evening which will cause poor reception at night.
STATIC
AM static may be caused by power lines, electric fences, neon signs, and thunderstorms. Static may become very noticeable if the AM station is weak or distant.
AM Signal Issue - Diagnostic Tips
First, it is important that you compare the reception performance of the complaint vehicle with the reception performance of other vehicles with known good reception. Use the same set of test stations in the same locations when you test the vehicle, in order to become accustomed to how the stations should sound and what external interference is to be expected. This should be done with the engine running and with the engine not running in the same location.
It is important to note that even with a perfect AM radio receiver and a perfect antenna, reception conditions are constantly varying. Interference from noise sources, both internal and external to the vehicle, are often erratic and unpredictable.
The most important tool used in diagnosing AM radio concern is a reliable weak AM signal source. A high-power AM Broadcast station one or two hundred miles away is ideal. The station should be clear so that you can understand what is being said with little or no difficulty.
It is important to note that there are other sources of noise, external to the vehicle, that can interfere with the signal you are trying to receive. These external noises should be either taken into account or avoided. For example, power lines, transformers or fluorescent lights can radiate noise in the AM broadcast band. It is best to test the concern vehicle in an area well clear of such noise sources.
Summary:
Select a set of test stations, especially the stations that may be the reason for the customer concern, and some which are over 100 miles away.
^ Note the reception performance of a known good vehicle in the desired locations. Note the presence of any local external noise sources (eg. power lines, etc.).
^ Compare the performance of the concern vehicle when receiving the test stations in the same locations.
DIAGNOSIS
If a vehicle's audio system has been verified to have an AM fading or static concern that is not found in a comparably equipped vehicle under similar conditions, perform the following diagnosis.
VISUAL INSPECTION
Poor AM radio reception may be caused by poor antenna cable connections at the various antenna cable connectors, and/or at the antenna base. Visually inspect all the connectors of the antenna system. This includes...
^ The antenna connector at the rear of the radio
^ The in-line antenna connector (if equipped)
^ The connector at the base of the antenna
^ The base of the antenna for signs of poor grounding (Some antenna bases "bite" into the underside of the fender for grounding. To ensure proper installation, refer to the appropriate Service Manual, Sections 35-10 or 15-02, depending on model year.)
^ The antenna for any loose screws or station nuts
^ Improper connections (repair if found and verify the effectiveness of repair).
CORROSION INSPECTION
Inspect all of the connectors of the antenna system. These include...
^ Connector at the rear of the radio
^ The in-line antenna connector (if equipped)
^ The connector at the base of the antenna
^ If there are signs of corrosion (severe discoloration, rust or white powder from the zinc die-cast bases) on any antenna components, repair the concern by replacing any antenna component where evidence of corrosion is found. Verify effectiveness of repair.
ELECTRICAL TESTS
Perform the following antenna conductivity/resistance diagnosis and testing procedures.
ANTENNA TEST # 1 - ALL ANTENNA TYPES
1. With the antenna installed on the vehicle and the cable unplugged from the radio, perform the following resistance tests with an ohmmeter. Probes must contact antenna at points specified by arrowheads in Figure 1.
2. If ohmmeter tests are satisfactory, the antenna is good.
3. If any ohmmeter is unsatisfactory, take the following action:
a. If it is a one-piece assembly, replace the complete antenna and cable assembly.
b. If it is a detachable cable and mast, perform Antenna Tests # 2 and # 3.
c. If it is a manual antenna with an extension cable, perform Antenna Test # 4.
ANTENNA TEST # 2 - ANTENNA EQUIPPED WITH DETACHABLE CABLE AND MAST
1. When the results in Antenna Test # 1 have been unsatisfactory, disconnect the antenna mast and base from the cable and perform the tests shown in Figure 2.
2. If ohmmeter readings are satisfactory, the antenna is good. Perform Antenna Test # 3.
3. If either of the readings are unsatisfactory, replace the cable.
ANTENNA TEST # 3 - ANTENNA MAST AND BASE
1. Perform the tests shown in Figure 3.
2. If ohmmeter readings are satisfactory, the antenna mast and base are good. Replace the cable.
3. If either reading is unsatisfactory, replace only the base assembly. The mast should be good.
ANTENNA TEST # 4 - ANTENNA WITH EXTENSION CABLE
1. When the results in Antenna Test # 2 have been unsatisfactory, disconnect the extension cable from the main cable and perform the tests shown in Figure 4.
2. If ohmmeter readings are satisfactory, the extension cable and main antenna cable are good. Perform Antenna Test # 3.
3. If either reading on the extension cable is unsatisfactory, replace the extension cable.
4. If either reading on the main antenna cable is unsatisfactory, take the following action:
a. If it is a one-piece assembly, replace the complete antenna and main cable assembly.
b. If the main cable is detachable, perform Antenna Test # 2 and # 3.
Service as needed per the appropriate Service Manual, section 35-10 or 15-02. Verify the effectiveness of the repair.
IN-LINE CONNECTOR
If diagnosis and repair procedures above have not been effective, the in-line connector of the subject vehicles may be intermittent. Service it as outlined in the following repair procedure.
STATIC CONCERNS - ALL RANGER, BRONCO II AND EXPLORER VEHICLES
1. Remove the radio. Refer to the appropriate Service Manual, Sections 35-01 or 15-02, for removal procedure.
2. Disconnect the antenna cable at the in-line connector located above the glove box.
3. Unbolt the in-line connector from its mounting location above the glove box. A 7 mm straight/open ended wrench can be used.
4. Remove the instrument panel portion of the antenna cable. Detach the antenna cable from the two locators, one to the right of the radio opening and the other behind the center heat duct.
5. Remove the antenna base and lead-in cable. Refer to the appropriate Service Manual for the removal procedure.
6. Remove the instrument panel using the appropriate Service Manual procedure.
NOTE:
THE HOLE WHERE THE ANTENNA PASSES THROUGH THE COWL IS JUST BELOW THE WINDSHIELD, ABOUT 4" (101.6 MM) FROM THE RIGHT SIDE. IT IS ONLY NECESSARY TO GAIN ACCESS TO THE HOLE, SO THE INSTRUMENT PANEL DOES NOT HAVE TO BE TOTALLY REMOVED FROM THE VEHICLE.
7. Replace the antenna cable with a one-piece cable provided in Service Kit (E3TZ-18813-B).
a. Route the new antenna cable through the fender and cowl hole.
b. Seat the grommet. See Figure 5 for details.
8. Route the new cable in the instrument panel along the same path as the original to the radio opening.
CAUTION:
DO NOT POSITION THE CABLE USING THE RETAINERS INCLUDED WITH THE ANTENNA KIT AS SHOWN IN THE ACCOMPANYING INSTRUCTION SHEET IS-5082-B.
9. Reinstall the instrument panel.
10. Reinstall the radio.
11. Install the antenna base on the cowl top outer panel per service Manual.
NOTE:
THE KIT INCLUDES A NEW MAST AND BASE COVER. USING THE NEW WHIP MAY CAUSE INCREASED WIND NOISE. THEREFORE, ITS USE IS NOT RECOMMENDED. THE BASE COVERS DIFFER ONLY IN COLOR, AND MAY BE INTERCHANGED IF THE CUSTOMER WISHES TO DO SO.
1990 CROWN VICTORIA/GRAND MARQUIS
1. Replace the existing antenna system with instrument panel cable (F1VY-18812-D).
2. Replace the antenna using the following components.
^ Power Antenna: F0AZ-18850-A
^ Fixed Antenna: F0AZ-18A984-A
3. Use the replace procedure outlined in the 1990 Crown Victoria/Grand Marquis Service Manual, Sections 35-10 or 15-02.
PART NUMBER PART NAME CLASS
F1VY-18812-D Instrument Panel Cable C
F0AZ-18850-A Power Antenna B
FOAZ-18A984-A Fixed Antenna C
E3TZ-18813-B Radio Antenna Service Kit AN
OTHER APPLICABLE ARTICLES: 91-5-5
WARRANTY STATUS:
Eligible Under Basic Warranty Coverage
OPERATION DESCRIPTION TIME
930205A Replace Antenna Assembly 1.3 Hrs.
DEALER CODING
BASIC PART NO. CONDITION CODE
18812 93
OASIS CODES: 207000