Why are my headlights dimming when braking? - Page 2 - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


1992-1999 Series I L27 (1992-1994 SE,SLE, SSE) & Series II L36 (1995-1999 SE, SSE, SLE) and common problems for the Series I and II L67 (all supercharged models 92-99) Including Olds 88's, Olds LSS's and Buick Lesabres Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

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Old 12-03-2012, 08:29 AM   #11
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Where is the link to the sense wire mod? Sounds interesting for sure!
I installed 1.6 watt brighter tail & brake lights in the PK ave which has something like 12 bulbs.

Definitely before I installed the Odyssey battery my headlights would really dim at stop or idle. That comes to the next problem, with all the draw like wipers,heater,radio, etc etc on, our small OEM alts are not able to keep up idle, that is why lights mainly dim & also a weaker battery sure wont help. I think the OEM ALt is only putting out about 60 amp max at idle (guesstimate)
Quality power can build them so you get lots of amp at idle:
GM CS130D high output replacement alternator
The Odyssey Battery keeps my lights bright though in most conditions.

I also converted the side post crap to top post connection. Used the stock cables as it had large holes already in the connections.

The odyssey load tested out new at a whopping 1219 CCA with Midtronics load tester.
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Old 12-03-2012, 09:38 AM   #12
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Old 12-09-2012, 07:13 PM   #13
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Yes, and if you look most new cars are at 14+, our cars run at 13. something normally, too low can damage components too. I can tell you in 4+ years of having this, I haven't had a single problem.
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Old 02-14-2013, 08:28 PM   #14
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Can I add this wire without buying the new plug and wiring it in? Today my car was sitting at the stoplights and it dropped to the top end of the red zone on the voltmeter in the dash. It has been doing this with a full load lately here in the winter (heater on high, radio on, headlights on, brakes on)
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Old 02-14-2013, 09:38 PM   #15
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Hey Cody:
>>>
"With the added voltage you can shorten the life of everything from light bulbs to your battery."
>>>

That is true - to a very minor extent. I have lost a great Die Hard battery due to a regulator getting weak and overcharging a battery. (Further down in the text I'll explain that 12 volts is *not* the optimal voltage.) However, I have a background in computers and electronics, and I know the worst thing for electronics and electrical components is operating at lower/higher voltages than designed, and even worse than that is a fluctuating power supply.

That being said - the sense wire for the voltage regulator is typically tied in to a place in the harness where it is cheapest and easiest for the manufacturer. Being that most accessories are driven from a two major feeds within the fuse panel (unless you have one of those cars with 3 fuse blocks - Alero comes to mind... WTF were they thinking?), one feed is switched by the ignition, the other feed is constant hot. There is a higher current draw from the fuse panel than there is, say, 2 feet away from the alternator.

I have read many documented cases of voltage drops and lackluster charging because the voltage regulator sense wire isn't seeing the same voltage as elsewhere within the electrical system. In the grand scheme of things, what may be a little net loss of battery voltage is compensated for by the higher RPMs of driving, and daytime driving where lights aren't used, and other low-demand times that make up for any deficiency.

I have this problem with my LeSabre, my charging system is running on the better side of spec (13.2-13.4 v)... But at night, for instance, my car is running 8 tail lights, 1 license plate light, 4 parking lamps, 4 marker lamps, 2 headlights, plus all the little #194s and #168s in the dash. When my radiator fan kicks in, it'* a quick 1.5-2 volt dip (motor startup surge). When I hit the brake or hit the turn signal, the voltage fluctuates.

It'* the nature of the beast. Typically speaking, DC (battery power) components last longer than AC (house current) devices because AC cycles positive-negative 60 times a second (in the US). Most household devices actually have a bridge rectifier (so does your alternator, BTW) inside to convert the AC to DC before running your computer, TV, iPad, cable box, etc.

Sorry, I kinda rambled... But essentially, having the sense wire physically and electrically closer to the largest sources of draw will ensure that your voltage regulator in the alternator bumps the charge higher when needed. As a result, your system-wide voltages will be more consistent.

Oh, and one more thing... Alternators put out (on average) 13.2-13.8 volts. 13.8 is necessary for proper charging of 12v batteries. So the closer you get your system to 13.8, and the more rock-solid that source is, the better off you are.

OK, there'* my $0.02.
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Old 02-14-2013, 10:02 PM   #16
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Quote:
Originally Posted by ahicks66 View Post
Hey Cody:
>>>
"With the added voltage you can shorten the life of everything from light bulbs to your battery."
>>>

That is true - to a very minor extent. I have lost a great Die Hard battery due to a regulator getting weak and overcharging a battery. (Further down in the text I'll explain that 12 volts is *not* the optimal voltage.) However, I have a background in computers and electronics, and I know the worst thing for electronics and electrical components is operating at lower/higher voltages than designed, and even worse than that is a fluctuating power supply.

That being said - the sense wire for the voltage regulator is typically tied in to a place in the harness where it is cheapest and easiest for the manufacturer. Being that most accessories are driven from a two major feeds within the fuse panel (unless you have one of those cars with 3 fuse blocks - Alero comes to mind... WTF were they thinking?), one feed is switched by the ignition, the other feed is constant hot. There is a higher current draw from the fuse panel than there is, say, 2 feet away from the alternator.

I have read many documented cases of voltage drops and lackluster charging because the voltage regulator sense wire isn't seeing the same voltage as elsewhere within the electrical system. In the grand scheme of things, what may be a little net loss of battery voltage is compensated for by the higher RPMs of driving, and daytime driving where lights aren't used, and other low-demand times that make up for any deficiency.

I have this problem with my LeSabre, my charging system is running on the better side of spec (13.2-13.4 v)... But at night, for instance, my car is running 8 tail lights, 1 license plate light, 4 parking lamps, 4 marker lamps, 2 headlights, plus all the little #194s and #168s in the dash. When my radiator fan kicks in, it'* a quick 1.5-2 volt dip (motor startup surge). When I hit the brake or hit the turn signal, the voltage fluctuates.

It'* the nature of the beast. Typically speaking, DC (battery power) components last longer than AC (house current) devices because AC cycles positive-negative 60 times a second (in the US). Most household devices actually have a bridge rectifier (so does your alternator, BTW) inside to convert the AC to DC before running your computer, TV, iPad, cable box, etc.

Sorry, I kinda rambled... But essentially, having the sense wire physically and electrically closer to the largest sources of draw will ensure that your voltage regulator in the alternator bumps the charge higher when needed. As a result, your system-wide voltages will be more consistent.

Oh, and one more thing... Alternators put out (on average) 13.2-13.8 volts. 13.8 is necessary for proper charging of 12v batteries. So the closer you get your system to 13.8, and the more rock-solid that source is, the better off you are.

OK, there'* my $0.02.
I want to first off thank you for that excellently detailed reply. That helps me understand current and the wiring perfectly, and now I see why the alternator needs the sensing wire.

Now, Is there a way to use my existing plug to add the sensing wire? I'm guessing one of the wires has to be the voltage detector, otherwise the alternator wouldn't know what the system voltage was, correct?

This is excellent information, and Ill have to do some checking on it again tomorrow if I can. It'* been snowing so I've spent more time on the snowmobile than I probably should... the joys of being inbetween jobs.. I beat everyone to the fresh snow on the trails!
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Old 03-09-2013, 01:32 PM   #17
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I have now added that alt sensing wire, and it still dims. ARGH. Looks like that specifically was not the problem. :(
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Old 03-09-2013, 01:33 PM   #18
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Im going to have to go through the testing procedure ahicks66 mentioned to see if I can isolate where the problem is.
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Old 03-10-2013, 09:21 AM   #19
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i dont remember did you try cleaning all your big connections for power and ground?
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Old 03-11-2013, 03:10 PM   #20
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Quote:
Originally Posted by jwfirebird View Post
i dont remember did you try cleaning all your big connections for power and ground?
yessir! I think I mentioned that in the beginning of all the stuff I have tried, and that was why I came to the board because it must be something I can't think of
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