Headlight logic

[JimP]

Hello Buick forumites. I bought a 2004 Lesabre Custom a couple days ago. It's a garage queen with only 106kmiles on the odometer. It feels and looks like a new car. I'm quite pleased.
Can someone explain the ins and outs of headlights?
I'm about to leave for a trip mid day. I want assurance that my headlights work since I'll be returning in the dark. I see this domed sensor on the dash. The manual says it is sensing ambient light.
Does it have a bearing on whether the headlights are on or not?
For the life of me, sitting in my garage, (some ambient light) I can't figure out how to get the headlights to come on. Car on or off, I tried covering the dome with a towel - nope. I messed with the two switches to the left of the steering wheel - nope. In/out of gear - nope WTF!
I have a VW that has stranded me on many occasion because it leaves the parking lots on if you turn off the key without manually switching of the headlights first They wash out in sunlight. Five hours later I can't start the car because the battery has run down.
Once the VW auto locked me out with the engine running - cost me big$ to break in. I believe both of these things are due to failing door switches. AI is OK if the sensors function well. If they don't, you are screwed.
I thought I was getting away from stupid automation buying a 2004 car.

 

[MelsRegal]

Page 3-14 explains how to turn them on manually on if you don't trust the Twilight feature.

 

[02LTD2.0]

These cars have an auto shut off feature that kills power after about 10 to 12 minutes to prevent running down your battery if you leave the lights on.

 

[DrivenDaily]

Press the headlight button. It's the one on the top. The one on the bottom turns on just the parking lamps.

When either the sensor, the parking lamp switch, or the headlight switch turns on the exterior lights, the little yellow LED in the headlight button turns on. It doesn't tell you whether the headlights themselves are on or just the parking lamps, but at least it tells you something.

I can get my 2005 to turn on the headlights in broad daylight simply by parking under the shade of a tree. I have also something sitting on top of the sensor, not realizing I had placed it there, and could not get the headlights to turn off. I finally realized my predicament, removed the item, and shortly after the headlights turned off.

If yours does not turn on the headlights automatically, then use the headlight switch until you decide to fix it.

 

[JimP]

Thanks for the info fellas. Page 3-14 is a bit vague about the behavior of the turn signal wand. One can rotate it for wipers but it is pulled back for the headlight function (left out of description) It is multi-function. Here is what I have learned via experimentation:
During daylight - Initially pulling the wand back turns the headlights on so long as the dash headlight button has been pushed previously and is lit. Further cycling the wand switches between high and low beams. To manually turn the lights off one must press the dash headlight button. I haven't experimented during the night time.

 

[DrivenDaily]

That T/S stalk is, indeed, multifunction!

During daylight hours when the headlights are not on, pulling it toward you (the driver) will engage the FTP feature — Flash To Pass. That's fancy-schmancy talk for flashing the high beams.

However, when you do, if you hear a click sound, that means that the next time the headlights turn on, you have also switched that mode from Low to High, or from High to Low, depending on where it was already at.

You can learn to pull it only enough to see the High Beam indicator, a blue icon to the left of center, next to the left turn signal indicator.

 

[jackiebelle1204]

Thanks for the info fellas. Page 3-14 is a bit vague about the behavior of the turn signal wand. One can rotate it for wipers but it is pulled back for the headlight function (left out of description) It is multi-function. Here is what I have learned via experimentation:
During daylight - Initially pulling the wand back turns the headlights on so long as the dash headlight button has been pushed previously and is lit. Further cycling the wand switches between high and low beams. To manually turn the lights off one must press the dash headlight button. I haven't experimented during the night time.

I also just acquired a 2004. Last night (first night drive) I accidentally turned the headlights completely off while going down the road by trying to dim my brights using the turn signal only. I need to experiment more but could this be some kind of electrical problem or just an ID10T error? Thanx in advance!!

 

[DrivenDaily]

I would say that the best way to figure that out is to turn the headlights on manually, then go look at both lights to see what is on and what is not.

On my 2005 (which seems to be designed differently by the factory than pre-2005 in some regard), the low beams turn on separately from the high beams, meaning that I can have either the lows OR the highs, but not both at the same time, unless I hold the FTP in the On position.

What may have happened to you is that the low beams are not working (bulb(s), fuse(s), relay, plug/connection, etc.) and you had the high beams on, then when you switched to low beams, there was nothing. Finding out you have no low beams on a dark road that you are not familiar with is not fun!

 

[02LTD2.0]

I also just acquired a 2004. Last night (first night drive) I accidentally turned the headlights completely off while going down the road by trying to dim my brights using the turn signal only. I need to experiment more but could this be some kind of electrical problem or just an ID10T error? Thanx in advance!!

That happened on my 2002 one night. I chalked it up to being a "glitch".

 

[jackiebelle1204]

It may just be a glitch...I was running with low beams but it happened when I tried to go back to low from high when meeting another vehicle...very weird! I was only using the turn signal control...

 

[DrivenDaily]

Ah, I see (pun intended). It's making more sense now!

The lows were already on and you switched to high beams. It was when you switched back to low beams that they did not come back on.

While the diagram below suggests that the HLD is either Low or Hi, it may not physically make contact with Low every time it switches back from Hi. This would explain what you describe.

The HLD switch may have been clicked just enough to turn off the highs, but did not click far enough to turn the lows back on. Usually, HLDs are designed so that there is an overlap to ensure that the switch is fully in one position or the other, and that both circuits are energized until the other turns off. It would seem that the designers got lazy and figured that while you're pulling the stalk toward you, the highs are on, but that's because the FTP turns them on, not the HLD itself.

I plan to modify my lights so that the low beams do not cancel when the high beams turn on. That way, the only lights turning on and off will be the high beams. The low beams will never turn off unless the headlight circuit itself is turned off. My simple plan is to add a diode between the 2 relay coils so the high beam coil energizes the low beam coil, but the low beam coil will not energize the high beam coil.

The full diagram shows that the DIM applies power to one side of each of the coils when it turns on the parking lamps, and the HLD applies a ground.

There are separate contacts for FTP. What the snip below does not show is that the FTP does not go directly to the high beam relay. Instead, it goes to the DIM, which then provides both power and ground to the high beam coil. Since the parking lamp relay's power is controlled on the same wire by the DIM, their relay does not get a ground signal during FTP so they do not turn on even though power is supplied to it when FTP. (Unless the parking and/or headlights are already on.)

Sorry for the long post, but the complexity of this design just blows me away, and I wanted to contribute information that is as clear as possible. Lemme know if I need to edit my post, or if anyone has questions. I'll try to explain what I think I understand.




Abbreviations:
DIM: dash integration module
HLD: headlight dimmer
FTP: flash-to-pass

 

[RD_Atlanta]

Insightful post, Driven Daily..