GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 1999 🢒 Eldorado 🢒 Body and Accessories 🢒 Lighting Systems 🢒 Headlight System Check

Step

Action

Normal Result(s)

Abnormal Result(s)*

1
  1. Turn the ignition switch to the OFF position.
  2. Place the gear selector in the PARK position.
  3. Place the twilight sentinel in the OFF position.
  4. Place the headlamp switch in the OFF position.

All of the exterior lamps are OFF.

2

Place the headlamp switch in the PARK position.

All of the park lamps light.

3

Place the headlamp switch in the HEAD position.

All of the park lamps remain lit. Both of the low beam headlamps light.

4

Pull the multifunction lever in order to place the headlamp dimmer switch in the HIGH position.

The headlamps switch from low beams to high beams.

5
  1. Place the headlamp dimmer switch in the LOW position.
  2. Place the headlamp switch in the OFF position.
  3. Turn the ignition switch to the RUN position.

All of the headlamps and the park lamps are OFF.

6
  1. Place the gear selector in the DRIVE position.
  2. Expose the ambient light sensor to bright sunlight or a bright incandescent light.
    • On the DeVille, both of the low beam headlamps light at a reduced intensity. All of the other exterior lamps remain OFF.
    • On the Eldorado, both of the high beam light at half intensity. All of the other exterior lamps remain OFF.

7
  1. Place the gear selector in the PARK position.
  2. Turn the twilight sentinel ON in order to place the delay in the minimum position.
  3. Cover the ambient light sensor.

Both of the low beam headlamps light at full intensity. All of the park lamps turn ON within 30 seconds.

Twilight Sentinel Inoperative

8
  1. Turn the ignition switch to the OFF position.
  2. Slide the twilight sentinel delay switch slowly from the minimum position to the maximum position.

The twilight sentinel delay changes from 3 seconds to 180 seconds in approximately 10 second intervals.

Twilight Sentinel Delay Inoperative

9
  1. Place the twilight sentinel switch in the maximum position.
  2. Turn the ignition switch to the OFF position.

All of the exterior lamps turn OFF after approximately 3 minutes.

Twilight Sentinel Delay Inoperative

10
  1. Turn the ignition switch to the RUN position.
  2. Expose the ambient light sensor to bright sunlight or a bright incandescent light.
  3. Turn the windshield wipers ON.

Both of the low beam headlamps and all of the park lamps turn ON after approximately 20 seconds.

Headlamps Inoperative - Low Beams with Windshield Wipers On

* Refer to the appropriate symptom diagnostic table for the applicable abnormal result.