CUSTOMER COMEBACKS FOR INOP. BACKGROUND LIGHTING

Subject: INOPERATIVE BACKGROUND LIGHTING CUSTOMER COMEBACKS

Model and Year: 1990-93 LUMINA

CONDITION:

---------- There have been some reports that all the background lights on the #8 circuit may become inoperative on the 1990-93 W-Car. Because this is an intermittent condition, the headlamp switch may be replaced more than once, resulting in customer comebacks. This bulletin offers a diagnostic procedure to find the cause of this condition and correct it properly.

The lights on the #8 circuit include: - Cluster Lighting - Radio Lighting - HVAC Controls Lighting - Power Window Switches Lighting - Power Door Lock Switches Lighting - Power Mirror Switches Lighting - PRNDL Lighting (with console) - Ash Tray Light - Headlamp Switch Lighting

NOTE: This condition affects only the background lighting portion of the headlamp switch. The headlamps and parking lamps will still operate properly.

CAUSE:

------ The electronic components in the headlamp switch that control the background lighting may be damaged by an intermittent short circuit before the fuse blows. If a headlamp switch must be replaced, but only the background lighting circuit is inoperative, the steps listed below should be followed. This is especially important if the headlamp switch has been replaced before on this vehicle. Section 8A-117 contains the wiring diagram for this circuit.

CORRECTION:

----------- Before installing a new headlamp switch, the wires in the #8 circuit (gray wires) should be examined for intermittent short circuits. The most likely areas for these shorts are the floor console wiring, the wiring inside the doors (especially in pass-through areas), and behind the instrument panel.

If a short cannot be located, the following procedure can be used to isolate the area of the short:

1. Remove the old headlamp switch. 2. Locate the two gray wires coming from the 106-way connector (C200) near the right hand kickpad. These wires are coming from cavities 2A (door switches) and 9N (console wires). 3. Splice and solder a one amp fuse holder into each of the circuits. The fuse holders are available from a local electronics supply outlet, such as Radio Shack. Their P/N's are: Fuse Holder, 270-1281, and Fuse, 270-1283. Equivalent parts can also be used. 4. Install a new headlamp switch. Test drive the car to see if the short can be reproduced. If the short does not reoccur, return the car to the customer. 5. If the vehicle returns with the background lighting out in either the door switches or the console, one of the fuses should be blown. Check that circuit for an intermittent short to ground, and replace fuse(s). If the headlamp switch background lighting circuit has failed again, and neither fuse is blown, then check the I.P. wiring for an intermittent short to ground, and replace the headlamp switch.

WARRANTY INFORMATION: Labor Operation: T3303 -------------------- Labor Time: 0.3 Hr. For installation of Fuses.

Use existing labor operations and times for repairs.

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.