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'87 Eldorado
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Discussion Starter #1
I bought my first Cadillac - 1987 Eldorado in really nice condition. I loved this car when it first came out - took only 20 years to get it :dance:

The person that owned it before me took pretty good mechanical care of it, but was not into "stock" items, i.e. the rearview mirror. It seems that it was replaced with a cheap manual one that came from an auto store and the wiring pigtail(s) were stuck up behind the map lights.

According to my owner's manual, the original rearview mirror was not only auto-dimming, but had the sensor in it for the auto dimming sentinel (automatic headlamp brightness on/off). I found another mirror like what was in the picture of my manual, and bought it off of ebay, but of course it has no effect on the dimming sentinel. Does anyone know if there were two different models if this kind of mirror, or if the mirror really did have anything to do with the dimming sentinel? The wiring diagram I got online through ALLDATA shows the dimming sentinel module with the photocell, but doesn't specifically say that it is part of the mirror.
I would really like to find another one to make this feature work. Everythine else in the car works now and it bugs me when something doesn't!

Thanks!
 

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2007 CTS White Diamond - 1997 Deville Silver Mist
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289 Posts
The auto dimming rearview mirror was most likely an option in 1987, not standard. I had a well equipped '90 Eldorado (basically the same style as yours) and it didn't have the auto dimming rearview mirror.

Regarding the dimming sentinel (also called Guidematic Headlamp Conrtol), this is the feature that switches the highbeams to lowbeams automatically when oncoming traffic is approaching at night. Your description made it sound like you were talking about twilight sentinel which is what turns the headlights on and off automatically.

Anyway, for the dimming sentinel, the sensor used to be located behind the grill. It looked like an electronic eye - I believe it was yellow in color. That's the way it was on my '82 Eldo. Unless they changed the location of this sensor to the rearview mirror in later years, I believe that it was always behind the grill. The twilight sentinel sensor is located on the center of the dashboard between the defrost outlets. This is what detects when it's dark or light outside and will turn your headlights on or off automatically.
 

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2005 White Diamond STS N* 1SF RWD ACC/HUD
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My 91 STS has the twilight sentinel but not the automatic high beams. The auto-dimming rearview has two photocells on it one in front to see if it is dark outside and one on the mirror to see the bright lights behind. I had the auto high beams on my 83 Eldorado...nice idea but didn't work very well...kinda like the V8-6-4 motor.
 

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'87 Eldorado
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7 Posts
Discussion Starter #4
Thanks for your response - I will check it out. I have had the grill off before and didn't notice it was there, but wasn't looking for it either. I'll see and let you know.
Thanks!
 

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'87 Eldorado
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7 Posts
Discussion Starter #5
I pulled up the wiring diagrams for this car, and it shows that the auto dimming sentinel photocell connector is in the windshield header, and sure enough I found it behind th maplights. Apparently there was either a 3rd photocell on the auto dimming mirror for the dimming sentinel, or another unit altogether that this pigtail plugged into that is missing. I guess I am just out of luck.
Thanks guys!
 

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2005 White Diamond STS N* 1SF RWD ACC/HUD
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Unless you drive primarily on two-lane country roads, the thing CONSTANTLY changes between low and high beams driving in the city, which in turn gets you flashed by pissed off oncoming drivers. At least that was my experience with my '83 Eldorado. I kept it turned off. I know how you feel, however, because I want everything to work on my car too. My car was orginally equipped with the heated windshield, but I'll be damned if I'll pay over $2000 for one.
 

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1988 Coupe Deville, 1991 Coupe Deville, 1989, 1994 Eldorado
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160 Posts
If your car had the dimming sentinel option then there would be a control for it above or below the twilight sentinel control switch, to adjust the sensitivity... one switch would say twilight sentinel the other would say dimming sentinel... if your vehicle does't have the dimming sentinel switch then it does not have the option.
 

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2007 CTS White Diamond - 1997 Deville Silver Mist
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289 Posts
As I mentioned before, I had a '90 Eldo for about 5 years and I really liked that car. I personally like the style of the '86 - '91 Eldos. I know some people think they're too small, but I thought they were nice looking cars.
I really liked the interior/dashboard of that car. It's very high tech.
The '90 had the 4.5 liter engine with Port Fuel Injection, so it was pretty powerful. How's the engine on your car? The '87 had the 4.1 liter engine, but I heard they were improved somewhat in the later years ('87 was the last year of the 4.1). Also, since that year Eldo is smaller, the engine doesn't seem to be that undersized for that car.
 

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'87 Eldorado
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7 Posts
Discussion Starter #9
Yes, my car has the dimming sentinel control on the dash, but no sensor. I purchased a used Service Manual off of Ebay which is filled with a tremendous amount of great info - I found a diagram that shows there is a little box (or should be) mounted with the rearview mirror that has the photocell and related circuitry in it for the dimming sentinel. It's not actually part of the mirror itself as far as I can tell. Oh well. I doubt I would ever actually find a replacement one. Thanks to all for your replies.

As far as the 4.1L engine, it's OK. It lacks get-up-and-go from a dead stop (in my opinion) but does great for passing and such.
 
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