Headlights - Remain On In Daylight

91caddy02
Bulletin No. T-91-59


File in Group 9

Number 76

Corp. Ref. No. 119004

Date March, 1991




SUBJECT: HEADLIGHTS REMAIN ON IN DAYLIGHT


MODELS AFFECTED: 1991 DE VILLES AND FLEETWOODS


Some 1991 DeVilles and Fleetwoods built prior to VIN breakpoint 252971 may experience headlights remaining on in daylight conditions when the twilight sentinel switch is on.


This condition may be caused by improper assembly of the twilight sentinel photocell. The photocell bracket may be rotated on its screw allowing the photocell to be partially covered by the instrument panel upper trim pad. This will cause the photocell to detect darkness at all times.


To repair this condition use the following procedure:


1. Remove the instrument panel upper trim pad, refer to Section 8C in the Service Information Manual.


2. Loosen the screw retaining the bracket to the instrument panel.

Figure 1 - Photocell Installation:

3. Rotate the bracket so that the flat end rests in the U-shaped notch in the bracket retainer. Refer to Figure 1.

4. Tighten screw and replace instrument panel upper trim pad.


If, after adjusting the photocell, the headlights remain on in early daylight hours or before dusk, verify the operation of the photocell. Measure the resistance while the photocell is shielded from light and while shining a bright light (a flashlight is preferred) on it. The resistance should be less than 35K ohms in bright light and greater than 95K ohms in dark conditions. If the photocell is not operating correctly, replace it with P/N 914032.


Check photocell circuits 278 (white wire) and 803 (black/white wire) for opens. Also, check circuit 10 (yellow wire) from the twilight sentinel module pin F and light switch pin B to the headlight dimmer switch for a short to voltage.


Verify that the resistance to ground on twilight sentinel amplifier ground circuit 803 (black/white wire) less than 1 ohm.

If the photocell and associated wiring operates correctly, the cause may be the twilight module; replace the twilight sentinel amplifier module, P/N 16515789.

Parts are currently available from GMSPO.

WARRANTY INFORMATION VEHICLE SERIES

Operation

Operation Description Number C D E J K V

Module, Twilight Sentinel - Replace R4220 .8

Sensor, Twilight Sentinel - Replace R4230 .3

Sensor, Twilight Sentinel - Adjust T6517 .3