Audio System - Troubleshooting

9220isuzu01

BULLETIN NUMBER
SB92-13-001


ISSUE DATE
March 12, 1992


GROUP
ACCESSORIES


AUDIO SYSTEM TROUBLESHOOTING


AFFECTED VEHICLES

All Isuzu models equipped with radio/cassette player or compact disc player.

SERVICE INFORMATION

Many audio systems returned under warranty are later found after inspection to have no defect. This Service Bulletin contains procedures for troubleshooting radio, cassette player and CD player problems.

SERVICE PROCEDURE

1. General Audio

a. Intermittent Conditions (the problem "comes and goes")

- Ask the customer to specifically identify the problem (abnormal noise, failure in all modes, etc.)

- Try to reproduce the intermittent condition, duplicating similar road or operating conditions under which the customer experienced the problem.

b. Noisy Conditions

Check for:
- antenna lead grounded
- battery terminals tight and secure
- radio chassis grounded
- chassis harness securely connected to radio
- harness from radio to CD player securely connected

c. If comparing the problem audio system with a system in another vehicle, be sure to compare the same type audio system and operating conditions.


2. Radio Reception

Poor radio reception may be caused by factors other than the radio or antenna, such as the strength or distance of the radio station. AM reception is very sensitive to static from power lines, traffic lights, electrical signs, electrical storms in the area, windshield wipers on the glass, and electric motors operating the power windows, door locks or windshield wipers.

FM radio signals can be blocked or reflected by tall buildings or mountains. Sometimes the antenna picks up a direct signal and a reflected signal at the same time, causing a distorted sound.

AM radio signals bend around obstacles and are less affected by tall buildings and mountains. This may increase the range of an AM station dramatically and cause interference (station mixing) between two stations that broadcast at the same frequency from different locations.

If reception on AM stations is weak, substitute a test antenna and lead. If reception is then normal, replace the antenna. If reception continues weak, replace the radio with an exchange unit from the appropriate radio manufacturer. Refer to the Isuzu Service Policy and Procedure Manual for details on radio exchange.

If customer complains of weak reception on FM stations, compare the reception on another radio. If a noticeable difference is heard, replace the radio with an exchange unit. If reception is the same, demonstrate comparison to the customer.


3. No Sound from Radio

a. Check fuses and replace if necessary.

b. If only AM radio reception is dead, check the antenna plug and repair or replace if necessary.

- If problem still exists, install a test antenna. If AM reception is then normal, replace defective antenna.

- If problem still exists, replace the radio.

c. If only FM radio reception is dead, replace the radio with an exchange unit.

4. Cassette Player

The quality and condition of the tapes used will affect cassette player performance:

Before using a tape, it should be checked for slack. If necessary, insert a pencil in the sprocketed hole in the tape reel and turn it until the slack is removed.

When not in use, tapes should be stored in their plastic cases to protect from dust, etc. Tapes should be kept away from magnetic objects, to protect from accidental erasure or deterioration. Exposure to extreme temperatures causes the tape to expand and contract, which packs the tape tightly on the reels. This will cause the cassette player to continuously switch into "Auto Reverse." To eliminate this problem, fast forward and rewind the tape to loosen it on the reels.

Extreme heat can soften the cassette label adhesive and cause the label to curl up. Loose or curled cassette labels can cause the cassette to jam inside the player. Also, extreme heat causes the tape oxides to stick and contaminate the player tape path, resulting in poor sound quality


and erratic tape speed, which may cause the tape to get caught on the roller or capstan. Using a head-cleaning cassette tape helps to maintain player performance and prevent tape damage.

Cassette Troubleshooting

If no sound when playing:
- Check for an obstruction behind the tape door.
- Test with a known good tape.
- If problem still exists, replace radio/ cassette player with an exchange unit. If abnormnal noise or weak:
- Inspect and clean capstan head with cleaner.
- Test with a known good tape.
- If problem still exists, replace radio/ cassette player with an exchange unit.

5. Antenna

a. Manual or power antenna: Fully extend and re tract mast antenna several times. If it does not extend and retract normally, clean the antenna shaft and apply WD-40 lubricant or equivalent. Retest antenna operation and replace if necessary.

b. Power antenna only: Connect a 12-volt power supply to the antenna motor to simulate radio on/off operation. Then:

- If the motor does not run, check the wires and terminals for looseness or damage. Repair or replace as necessary.

- If the motor runs but the antenna does not operate properly, check the antenna for damage. Replace if necessary.





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Compact Disc Player