Audio - Ignition Noise Audible Over Speakers

Group Ref.: Accessories

Bulletin No.: 319601

Date: October, 1993

SUBJECT:
IGNITION NOISE AUDIBLE OVER BOSE RADIO SPEAKERS
(REPLACE AMPLIFIER OR EXCHANGE RADIO RECEIVER)

MODELS:
1993 CADILLAC ELDORADO AND SEVILLE

This bulletin is being revised to change the cause and to add a second repair procedure. Please discard previous publications:

Cadillac T-93-61

GM of Canada 93-9-115

Some 1993 Eldorados and Sevilles equipped with both the Northstar powertrain (L37 or LD8) and the Bose radio (U1G) options may experience a noise condition over the radio speakers that may be described as a "ticking", "crackling", "buzzing", or "static" noise that usually occurs at engine idle and at low volume settings. The noise is primarily heard over the front speakers and will occur in all audio modes:
AM, FM, CD, and tape. The noise condition may not be present at engine speed greater than 1500 rpm.

This condition may be caused by the electrical noise generated by the ignition system that is detected by the Bose amplifiers and the radio receiver. New amplifiers (in production since breakpoints 607486 and 813446 for Eldorado and Seville, respectively) and receivers are available to correct this condition.

To determine if this bulletin applies to your application, use the following diagnosis procedure:

1. Turn all accessories to the "OFF" position. With the key "ON" and engine "OFF", turn the radio to the minimum volume setting.

2. If the noise is heard, then this bulletin does not apply to your application.

3. Start engine.

4. If the noise is heard, then this bulletin does apply to your application. Determine which speakers exhibit the condition.

To repair the condition follow this procedure:

1. For vehicles built after breakpoints 607486 and 813446, skip to step 2. This is the breakpoint for putting the revised amplifiers into production. For vehicles built before this breakpoint, replace the amplifiers of the speaker pair that exhibits the noise. The speaker amplifiers of the speakers must be replaced in pairs (both fronts or both rears). For example; if the right front speaker exhibits the condition, then both the left and right front speaker amplifiers must be replaced. The amplifier part numbers are:

Front Rear

Seville: 16193505 16193506
Eldorado: 16193503 16193504

2. Exchange the radio receiver, requesting a receiver with revision level E or higher, per Delco Technical Document Number RD93TBA09.

Parts will be available from GMSPO on October 18, 1993.