: Repairing the 1991 Eldorado / Seville Twilight Sentinal Photo Cell

11-06-10, 02:51 PM

Interior lamps will not automatically illuminate ever.
Headlamps will not illuminate automatically at dusk.
Body Data test BD44 does not respond to changes in lighting conditions.

What I did:

Removed factory photo cell assembly by unplugging it from the harness.

Purchased ($2.95) RadioShack item# 276-1657 (package of 5 assorted photocells)

Carefully removed the original can type photocell from the blue plastic housing. Yes there is a little door on the housing that will likely break off as you attempt to open it. No big deal if it does. DO NOT BREAK OFF THE BLUE HAT on the top of the housing as it is required.

From the RadioShack package 276-1657 I selected a medium sized photocell, they are not marked in any way nor do they have any polarity markings on the cells. In the package there are two large, two medium, one smaller than medium, and a tiny cell. As stated, I used a medium sized cell.

Next, I removed the old phtocell from the wire harness by desoldering it, then soldered the medium cell (uncut) to the original wire harness.

Next I placed the harness back into the Blue Housing securing it with electrical tape, then plugged it back into the lighting circuit. I did NOT secure the housing to the dash at this time as I had no idea if it would work or not.

Next, I ran the Body Data test DATA... test BD44... URIKA! uncovered it measured 4 and covered it measured 94... WOW ... right in specification according to the FSM. The headlamps also illuminated when the cell was covered.

Next, I fully assembled the unit into the dash, replaced the defroster vent and tried it again with IGNITION ON, MOTOR OFF.... since it was daytime, the interior lamps did not illuminate when the door was opened. I covered the center dash with the FSM... waited about 10 seconds, the headlamps came on... YAY! I rechecked the Body Data test BD44 one more time and the range was perfect.

I cleared the historical codes from the previous failed twilight photocell..
(B119,B120) and all is working fine now...

For how long? I don't know.. I just completed this today.

12-12-11, 11:22 AM
Found this thread via Google - A big thanks!

Car was behaving as if it was always daytime. No panel dimming, no interior lights, constant HEADLAMPS ARE ON messages. I didnt know there was a diag check for the photocell. 6 to 25 was the largest range I could get out of it. Bingo! Disconnected the cell and panel dims as it should, and lights come on when door is opened. Sweet. I'll see how she behaves with the cell removed since I dont use the sentinel anyway, otherwise I will try the radioshack trick.

Old thread but just wanted to say thanks for taking the time to post!