UNDERHOOD LAMPS INOPERATIVE OR STAYING ON (DIAGNOSIS)

VEHICLES AFFECTED: 1984-90 CORVETTES

CONDITION:

Underhood lamps that are inoperative, or that stay on.

CAUSE:

May be due to one of the following:

1. Mercury switch disengaged from retaining clip in lamp housing.

2. Mercury switch partially disengaged, and shorting across terminals.

3. Mercury switch has either short or open circuit internally.

IMPORTANT: If required, a new mercury switch P/N # 16503204 is now available. IT WILL NOT BE NECESSARY TO REPLACE COMPLETE LAMP ASSEMBLIES TO REPAIR THE ABOVE CONDITION.

CORRECTION:

Prior to making any repairs, make sure that the fuse and bulb are good, and that the wiring connectors under the hood are connected.

1. Raise hood to the full open position.

2. Remove the lens from the lamp assembly.

3. Inspect to insure that the mercury switch is in the proper position.

IMPORTANT: If switch is in proper position, check the switch and bulb with a 12v test lamp for continuity.

4. With lamp now operating, slowly lower the hood to inspect that the lamps turns off with the hood almost closed.

IMPORTANT: If lamps are still on with the hood almost closed, the mercury switch may be shorted. Replace the switch with P/N #16503204.

5. Raise the hood to full open, and anply a bead of 3M #08670 T3 Silicone, Permatex #26B High Temp R.T.V. (or equivalent) across the switch and clip ends for retention as shown in the illustration.

6. Reinstall the lens to lamp housing and carefully close hood. DO NOT SLAM HOOD CLOSED.

IMPORTANT: Some FLICKERING of the lamps may be noticed when raising the hood. This IS A NORMAL CONDITION and lamps should not be replaced or repaired for this condition.

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.