Twilight Sentinel won't switch on, or stay on
 

This is weird: my twilight sentinel is getting more sensitive to light, to the point that the Bonneville needs basically total darkness before it will turn its lights on. Last night was the worst: I'm sitting at a traffic light at a brightly-lit intersection, and the car turned its lights _off_ just as the signal turned green!

I mean, I could imagine the system maybe getting _less_ sensitive to light as it ages, and maybe turning its lights on too often on cloudy days or something, but this is the opposite: it's getting hypersensitive instead.

Before I wade into the service manual, can anyone tell me which component is most likely at fault here? I hope it's not the light sensor itself because it looks like I have to take out most of the gauge cluster to reach up back there.

Are you sure you weren't under any bright lights? Or is this happening under all circumstances? It is really odd to see it fail in this manner. Yours is the first I've heard of failing at all except for broken switches, which are fairly common. I'd hope yours is just the sensor. It's probably the cheapest part in the system.

Isn't the twilight sentinel sensor housed underneath the defroster grille across the dash? Or did they change that for 92 and on?

It looks easy to do, granted I'm right on the location.

I hope its not a big deal, the sentinel is handy when it works.

The twilight sentinel sensor is near the VIN plate at the front left corner of the dash, looks like a little recessed button. It is _not_ the tinted dome-like thingy sticking up in the center of the dash; that is the sunlight intensity sensor for the electronic A/C.

I've had the car since 1996 and this system has always worked perfectly. It's only gone weird on me in the past few months, so I know something is failing somewhere; I'm just kind of stuck for a starting point here, and was wondering if anyone else has seen this same problem.

I'm going to argue with you. Every GM car ever built with the twilight sentinel has the same dome sensor. Chrysler is the same too. That IS your twilight sentinel sensor. The one near the center of the dash. You can actually trick that sensor into turning your headlights on in broad daylight with black electrical tape. I've done it.

I just looked in the service manual. The twilight sentinel photocell is the one on the left side of the dash.

It's not that hard to remove. All you have to do is take the defroster grille off, then twist the socket 1/4 turn from the grille, and then unplug the photocell from the socket.

The resistance of the photocell should change from 15k ohms in bright light to 20M ohms in darkness.

I looked at the photocell diagram for the climate control, it shows it in the middle.

Oh, it services from the _top_? Is the grille held in with spring clips or do I need to look for screws to remove?

Great; will check that out.

...which reminds me that this spring I really want to get the leaky ol' evaporator replaced. Got a tax refund on the way and I am _not_ going to broil through another summer...

That dome in the middle ISN'T the photocell? I'm certain my older Buick Roadmaster and Olds Cutlass were that way! I've been wrong all this time, and nobody corrected me until now? :evil:

I was going to say will, I don't believe I even have a dome in the center. Maybe I'm wrong, I'll have to check when i get done with school today.

I always thought that the dome was the sensor/signal receiver for the keyless entry when factory installed. Kinda like an antenna, some have pretty red flashing lights.

The aftermarkets are usually window pillar mounted antenna.

My sentinel no longer works either. Is it dirty or do I have to replace it? Will? do you have a part number for an 89?

hahah I've learned when in doubt, go right to the willwren source!!