Twilight Sentinel Malfunction - '89 Deville

[guyslp]

Hello All,

         Let me preface this by saying I did do a forum search on "Twilight Sentinel" and looked through the results, but nothing jumps out at me as having the "same configuration" as my issue, at least not with a quick review.

         First, let me say that I just had the alternator replaced at the end of last week, and this problem just started in earnest two days ago.  However, there was a precursor event about a week and a half ago that I think must be related, and that was with the old alternator.   My lights work perfectly normally when you pull out the manual stem control.

         The precursor event was that while I was driving home after dark all of a sudden my lights went out.  Once I turned them on manually then promptly pushed the stem back in they were on again and stayed on again for the remainder of that trip and the Twilight Sentinel continued working just fine until it stopped working entirely.

         The Twilight Sentinel did work for about 5 days after the alternator was replaced, so I'm doubting it's related to that, but it still could be.  It has just stopped functioning entirely.  Based on the precursor event, my gut is telling me that this might be a failure of the photoelectric light sensor that's mounted in the driver's side speaker grate.  I base this mostly on the precursor event and the fact that things work 100% normally when the stem control for the lights is used.

          All of the above being said, I know very well that there may be someone or a number of someone's here who've "been there, done that, got the T-Shirt" and that the "got the T-Shirt" part may have absolutely nothing in common to what my gut is telling me.  So, if members of the cohort have something to offer based on their own experiences with this or far better knowledge of the Twilight Sentinel system than I have please do share.

[OldCadTech]

Since I have slept a couple of times since '89, please send me a picture of the top of your dash. I don't remember the photocell being in a speaker grille. I remember it in the center of the dash, close to the W/shield.

[guyslp]

Your wish is my command.  There is nothing at center dash (though that's the arrangement on many GM cars) and the right side speaker grille does not have that opening.  I think that might be the wires from that photoelectric sensor that you see through the speaker grille in the photo.

 

 

[OldCadTech]

Pull the speaker grill and make sure the sensor is connected. Do you have a DVOM? ( Digital Volt Ohm Meter ) With the sensor disconnected connect the DVOM (on ohm setting) shine a very bright flashlight onto the sensor and check for resistance change. If none to very little change replace sensor. I don't remember the exact range but seems like it was quite a range.

[guyslp]

OldCadTech,

           That's on the list, but based on the service manual the actual connection for this is at the Twilight Sentinel Amplifier (or ECU if you prefer) and that's behind the dash much further down.

            

 

My car does not have airbags and based on the above wiring diagram it seems to me the possible failure modes would be:

1. Fusible link (definitely not)
2. Fuse 14 (definitely not since lights work manually)
3. Ignition switch (definitely not)
4. Light Switch (definitely not since lights work manually)
5. Twilight Sentinel Amplifier (possible, but not my first assumption)
6. Twilight Sentinel Control (possible, and could be at fault)
7. Twilight Sentinel Photocell (my first guess as to the culprit)

If there's something I'm missing please let me know.  Thanks for your input so far, it is sincerely appreciated.

[Logan]

I've had a couple of the twilight photocells shift in calibration as they age. Everything is fine until there are lots of overhead street lights...like near a shopping mall kind of situation....The lamps would suddenly turn off... A fresh sensor will likely fix your issue.

[guyslp]

Thanks Logan.

I also presume that this particular part cannot be all that expensive given what I know about photoelectric sensors in general (a very similar one is on night lights).

[rockfangd]

hmm. Hopefully yours is like a 194 bulb socket.

It is a expensive little part but will likely last a long time.

I had to put one in my Deville last year because it was not turning on the headlamps, domelamps, dimming the IPC..... All of the other stuff it cotrols.

once replaced all was back to normal.

[guyslp]

Well, I'm having difficulty finding a source for the part, either OEM or aftermarket, which is no surprise for a 28-year-old car.

That being said, someone must know what the tech specs are on the photocell that's used in this thing and it's easy enough to replace just that.  These can be obtained from a wide variety of electronics suppliers.

If anyone does happen to know the tech specs for the output please, please share them!

 

[OldCadTech]

More often than not it is the photocell, BUT it can be the headlamp switch, it controls power on the Red circuit #279 to the amplifier and the photocell. Manually moving the light switch by-passes the twilight sentinel function. If you have a DVOM you can check the switch and eliminate it.

So 4. - 5. - 6. & 7. are all possibilities. I would check for a replacement photocell at a wrecking yard or auto recycler - if you want to be politically correct.

So what is on the list - the DVOM?

[guyslp]

OldCadTech,

          Yes, what's on the list is checking things out with my digital multimeter (which, of course, includes a resistance feature).

          I'll call around my local (and not so local) auto salvage yards to see what I can find.

[guyslp]

See the topic, Dash Upper Trim Pad Removal - 89 Sedan de Ville, for details on removing the dash upper trim pad to get access to the photo cell of the Twilight Sentinel.