Haunted headlights on my 96 Park Ave

[smitty55]

Seems a bit strange to ask an automotive question on an outdoor site but that's what's cool about this forum and sets it apart from the others. Definitely the weirdest thing I've ever come across in my 45 years of car and truck ownership. I know there's some knowledgeable folks in this group so here goes.
96 Park Ave ultra. It's been sitting for a few months due to brake line leakage and lack of funds for a proper repair instead of another patch, but is normally a daily driver. A while back the headlights only would come on by themselves at night or maybe even during the day and turn off after a while, it was real intermittent. It has now got to the point that the lights are coming on more regularly and staying on for at least two minutes each time. It's draining the battery in two days now so the battery is now disconnected and charging. Maybe that will reset something.  I also worked every possible switch and slider related to lights many times. In fact as I discovered two nights ago if I work the headlamp switch on the door on/off while it happening the lights will go out. But then a while later it starts to cycle again. From some research I know there's a control module involved and also that twilight sensor failure can cause funny things to happen, but I never saw anything that had the on/off cycle as the principle symptom mentioned. So any insight would be well appreciated, I'm pretty comfortable in repairing things, I started working on aircraft instrumentation in the mid 70's right after high school where I also took electronics, so I've always used meters and test equipment since then.

Cheers

 

[DanD]

I'm not sure what or where to start with this? All I can say is that if you find the issue you may not want or can't fix it. Many of the parts for this system have been discontinued and the pieces that are available are crazily priced. For example the headlight dimmer switch (multi function switch style) is $600.00 plus. If the problem turns out to be the control module; it's a dealer only item that I cannot get a price on because its discontinued?

My suggestion is to rewire the lights, using another switch, and an old style floor mount dimmer. Under $50.00 and your time is all it'll cost you. You can use the original 20 amp circuit breaker for the headlight's power feed. You'll find this breaker in the under hood fuse panel; that's on the center of the firewall. Let me know what way you'd like to go and I'll try and help.

Dan.

[OhioFisherman]

 

[smitty55]

Tks guys. I haven't solved the mystery yet but I'm to the point where it isn't doing it for now at least

OF that guys soldering technique leaves a lot to be desired. Soon as I saw the soldering iron I was like what the hell, the tip isn't even properly tinned, it should be shiny silver color. Sure enough you can see there was no heat transfer, it wouldn't even melt the solder on that resistor thruhole so he could use the solder sucker on it. Solder wick would have helped at least it has some flux in it. Speaking of flux I never saw him use any when he replaced the resistor, or specially when he touched up that heated pin joint at the end of the board. That would be a fail on any soldering test for sure. But he did fix it so I give him that.

Dan I appreciate the offer, tks man. I highly doubt that MFS is at fault here, all functions on it work fine including the brights switch. For that matter all normal light related functions work fine including including warning beeps when I have the door open and the running lights or parking lights are switched on. So today I hooked the battery back up and the issue was still there and chronic so I went through the regimen again of thoroughly working all switches and sliders  related to the lights. I've had this car for 6 years now and these switches and pots have never been used, so that's never a good thing.  Well go figure I'm working the hell out of the headlight switch on the door while watching the headlamps. First time I hit it the headlights come on full, then next push lights are off. 10 seconds later daytime running lights come on and stay on, I didn't bother waiting to see if it would still cycle and I started working the headlamp door switch like 40 times and the twilight sentinel slider and it stopped happening. Then I noticed that if I put the Twilight Sentinel to the unmarked off position the running lights would come on again, like what the hell, but if I turned it on past the very light detent I could hear a relay click in the dash and the headlights would go off. After a couple of hours I went for a drive to work the brakes and came back and it happened again for a bit but again by working the two door switches and the sentinel system slider position I'm now close to 12 hours with no issues. It's not fixed yet, but at least a step in the right direction. There is one thing that stands out to me in all this, there is no way that that turning the twilight sentinel to off should turn on running lights with the ignition off. That symptom in itself points to the sensor system as the likely culprit. It could well be related to a high resistance contact somewhere too, not a component failure. Saying this, I can't see how a lighting system with no switches on would even have access to power with the ignition off in the first place, we're not talking dome lights here.
Cheers

Edited September 2, 2020 by smitty55

[DanD]

6 hours ago, smitty55 said:

I can't see how a lighting system with no switches on would even have access to power with the ignition off in the first place, we're not talking dome lights here.

No we're not talking dome lights; we're talking electronically controlled headlights. Oh yeah the dome lights are also controlled by an electronic module. (sorry had to point that out LOF) You have to think of these "switches" as inputs to the LCM; when you actuate one of these inputs; you are actually putting in a request to the LCM. The lamp control module (LCM) has two battery feeds that are hot at all times. A 20 amp fuse for the parking lights and a 20 amp circuit breaker for the headlights. So the LCM is possibly getting a skewed input from a failing sensor or "switch", an intermittent short/open in the wiring or the LMC is failing. Here's a wiring diagram; have at it.

98Buick.pdf

I loaded the diagram as a PDF as well as an image. The image is not very clear.

Dan.

Edited September 2, 2020 by DanD

[lew]

Your a  good man to have around Dan 👍

[smitty55]

Tks again Dan, that schematic is handy to have. Like Lew said you're a good man. I agree that there is power available to the parking and headlights as I can turn them on with the switches when the car is off. I still can't see how the running lights come on when the twilight sentinel is in the off position as that should be an open circuit to the AL Sensor. I'm definitely leaning toward the chance that there was some sort of skewed input from one or more switches as they hadn't been used since I got the car. Also since I worked the hell out of them yesterday I have had no issue with the running lights coming on. Again today I worked them to try and get a failure and no go, all is good except for them coming on when the sentinel switch is in the off position.  So far so good.
Now I need to find a shop that will do a brake line repair instead of a replacement for the time being. One  place said it was illegal to do so, first time I ever heard of that.

Cheers

[DanD]

I don’t think there’s a law on a patch repair on a brake line. It’s more of a liability concern. To patch a line a tech has to disturb the original line. You leave the shop with the patched line. Another section of that line blows causing an accident. The first thing out of most people’s mouths would be. Joe’s garage just fixed my brakes. Next thing Joe knows he‘s in court defending himself on a negligence charge. 
In my opinion it’s twice the work and materials to patch a line then replace it. I haven’t seen your car but being 24 years old it likely needs all the lines replacing? This is easy for me to say; but doesn’t safety mean more then a few extra bucks?

Dan. 

[smitty55]

I agree Dan, my first choice would be a full replacement, I had my 2001 Sierra done a couple of years back and it was $850. Money well spent in the long run and with the newer alloy tubing it will last as long as the truck easily.  As with any old vehicle there always comes a time to decide when to stop putting putting coin into the old boat. In this case the car is still in pretty good shape, even the rockers are still good, and I do like my big Buicks  ever since my first LeSabre back in the 80's. Actually a lot of the brake lines still look pretty good, I Krown it each year, but of course the leak is right where the clip is holding the pair running to the rear under my arse along a straight run. So I get it for sure, those lines are 25 years old, moving them around too much could be asking for trouble, but in this case it would involve minor line movement to plug in a properly flared patch line.  But yea I get it when it comes to shops being worried about liability.

Cheers