NOISE/POOR RADIO RECPT. ON AM (INSTALL NOISE FILTER)

SUBJECT: NOISE OR POOR RADIO RECEPTION ON AM 530 - 760 KHZ (INSTALL NOISE FILTER) VEHICLES AFFECTED: 1992-93 "E" AND "K" MODELS

THIS BULLETIN SUPERSEDES AND REPLACES CORPORATE BULLETIN REFERENCE NUMBER 219601.**

THIS BULLETIN IS BEING REVISED TO INCLUDE THE 1993 MODEL YEAR.

Some 1992-1993 model Eldorado and Seville owners may experience harsh audio system noise or poor reception on AM radio when tuned to stations between 530-760 kHz. The noise may be described as a "whine" or "growl" and may only be noticeable when the vehicle enters a poor AM reception area, such as beneath an underpass or into a concrete structure.

This noise may be induced through the 16 volt power feed from the instrument cluster to the radio control head vacuum fluorescent (VF) display. To diagnose the condition, move the vehicle to a poor AM reception area (indoors) for testing. The noise will be present with the key in RUN but not in ACCY, with RAP energized, or when the cluster fuse A5 in the trunk compartment fuse block is removed. The noise may change as dimming level is changed with headlights on.

To repair the condition use the following procedure:

1. Remove the radio control head as described on page 9A-36 of the Service Information Manual.

2. Install noise filter, P/N 1224205, in circuit 726 yellow at the radio control head as shown in Figure 1. With the key 'OFF", cut the yellow wire from connector C2, pin 5 at the control head. Strip the wire ends of each half of the circuit. Solder one of the yellow filter leads to each half of the cut circuit and cover with electrical tape. The third filter lead, containing an eyelet, should be attached under a radio chassis screw. Tape the filter to the radio harness to prevent rattles.

IMPORTANT: The filter must be installed in the direction as shown in Figure 1 to work properly. The correct orientation is for the black wire to be on the same end of the filter as the yellow wire that goes to the cluster.

3. Verify that the repair has remedied the condition. If not, diagnose the condition as above. If the condition still appears to be the caused by the 16 volt power feed, exchange the instrument cluster. If this does not eliminate the whine, continue diagnosis using Section 9A of the Service Information Manual. Do not back out the 16 volt line to the radio as this may result in the radio VF display being more dim than the other displays in the vehicle.

For vehicles repaired under warranty use:

Labour Time: .4 Hours

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.