HEADLITES ON 01 SEVILLE

[BOB W.]

The headlights on my 01 seville are on all of the time. This started about a week ago. The DRL lights are ok. If i move the sensor under the light switch to off I get the message HEADLIGHTS SUGGESTED. If I move it a little to the right, the headlights come back on .This happens on a sunny day,like yesterday.We don't get many of them in OHIO. I wonder if the sensor went bad.Has any body had this problem? THANKS

[BOB W.]

I forgot to say,that they the lights do go out when I turn the key off.

[Poobah]

If yours is like my '94, there is a sensor in the center of the defroster vent near the base of the windshield. It's either a small hole or a little plastic dome about 1/4" in diameter. If something is covering the sensor, or if the sensor is defective, the system can't see the sun and thinks it's dark.

[rek]

My headlights would come on too soon (daylight ). the dealer replaced the slide switch. That wasn't it. Then they replaced the sensor. That (sensor) fixed the problem. BUT, they goofed up the dash pad, when they lifted it to get at the sensor. They told me the area where the pad grabs , broke away. If you DIY, a thin blade, carefully used to release the dash pad, might prevent this. BTW, mine was done under warranty. Good Luck...

[Ranger]

It is not the "dome shaped sensor", that is the sunlight sensor for the A/C. It is the one next to it. If it is in the defroster grill like mine, the grill should pry up very easily for replacement. That most likely is your problem. Before replacing it make sure as suggested that it is not covered or dirty.

[wags]

If the rain sensor wippers are set to automatic it will turn on the headlights. Move the wipper control to off and the headlights should go off unless it is the sensor. Some states require headlights if wippers are on.

[rek]

Thanks for the "jog" Larry, my post should have said : They goofed up the dash pad when they lifted the DEFROSTER grill, to get at the sensor.

[RDWRIOR]

I would like to add the following comments to this discussion:

First, the post by "wags" concerning the automatic headlights switching on whenever the wipers are switched on is useful information. With the Rain Sense moisture-sensing wiper system, the wipers could be swtiched on but would not operate on a dry day, and the operator might not notice the wiper switch being left on except for the presistent "lights on" condition, which is normal.

That said, I do not believe it is the cause of the problem that Bob W. reported, because if it were I would not expect the 'HEADLIGHTS SUGGESTED' message to appear on the DIC when the Twilight Sentinel slider switch is off, which Bob reported he has observed in his vehicle.

Thus, I expect that the root cause of the problem is the ambient light sensor or its wiring, which is causing the module that "reads" the sensor to perceive constant darkness, regardless of the actual lighting conditions.

Bob W. - Unless you are experienced working on vehicle electrical systems and have ready access to a factory service manual for your vehicle, I would suggest that you have the problem properly diagnosed and repaired by a Cadillac dealership, or someone experienced in working on late-model Cadillac vehicles. Accessing the sensor is not that difficult if you know what you are doing. However, if the root cause is not the sensor itself, but a wiring problem, much of the instrument panel could require disassembly, which could be a very involved project.

Larry Grandolfo is correct that the ambient light sensor is mounted in the defroster grille, but is not the sensor with the "dome." (The "domed" sensor is for the automatic HVAC system.) However, unlike Larry's '97 vehicle, the defroster grille does does "snap in and out" on '98+ Sevilles. This grille part is secured with scews that must be exposed by removing the entire upper trim pad from the instrument panel. Removing this pad requires removing the four upper HVAC outlets (which requires some delicate work with a small screwdriver and a "hook" tool of some sort) and then removing a screw deep inside each outlet. Then the trim pad is lifted up and off by lifting the rear edge while pushing down on the front edges. This pad removal process is explained well in the factory service manual. Unfortunately, there is a mistake in the manual for the removal of the defroster grille part. The manual shows the actual drawings and "snap in/out" process for the earlier models, like Larry's, but this is NOT correct. Trying to "pry out" the defroster grille on a '98+ Seville will result in a broken grille and probable marring of the upper trim pad, both of which are very expensive parts. Trust me on this -- I learned about this service manual mistake the hard way!

(Fortunately, I was working on a GM test vehicle that was destined for the scrap heap, not my own vehicle. )

Apparently, the service manual was corrected sometime in the last year, but any printed manual from '98 - '02 probably contains the mistake for the defroster grille, so be warned.

Doing this sensor replacement job the right way is really not that difficult and requires no special tools, but you really have to know what you are doing first. This is why I suggest that Bob have the work done for him. And even if the work is done professionally, when it is done remember to inspect the HVAC vents, trim pad, and defroster grille to be sure that there are no boken or loose pieces, which might result from shoddy, "hurry up" work. I've seen that before, and the results aren't pretty.

Good luck!

[BOB W.]

Thanks for the info , RDWRIOR, I guess I will take it to a cadillac dealer,after the 10 inches of snow we got yesterday melts.I guess I am twice as safe driving it now, with the DRL and headlights both on at the same time.Thanks again. BOB W.

[RDWRIOR]

I guess I am twice as safe driving it now, with the DRL and headlights both on at the same time.

Bob,

I guess I didn't understand from your original post that you had headlamps and DRLs operating at the same time.

This should never happen, and I don't think that this condition can be explained simply by erroneous ambient light sensor data.

If you are indeed having both sets of lights operating simultaneously, it suggests an internal problem with the body control module (BCM). If that is the case, then it is an even better idea to have the problem diagnosed and repaired by a Cadillac dealership.

Please post the outcome of this matter.