96grandprix Posted October 20, 2010 Report Share Posted October 20, 2010 got a new to me 96 gp and one thing i noticed while driving at nite the headlights would always dim for a split second when i hit the brakes. kinda annoying.then i took a tailight apart to replace the water damaged outer lens. then i noticed the number of brake lights , 6. wow im thinkin thats wat is dimming my headlights when ihit the brakes. im gonna get some led replacements for the brake lites, itll b a lot less load. anybody else dealt with this? Quote Link to comment Share on other sites More sharing options...
white4d96 Posted October 20, 2010 Report Share Posted October 20, 2010 Mine dims the lights really bad when I have my hazards on, but I never noticed it from the brakes. Of course, being that I have HID headlights, I don't have headlight dimming, but every other light does =P I've wanted to do LED's in the tails, but haven't had the money to do so with decent bulbs. Quote Link to comment Share on other sites More sharing options...
tornado_735 Posted October 20, 2010 Report Share Posted October 20, 2010 I noticed it on mine, just the nature of the beast. Quote Link to comment Share on other sites More sharing options...
RobertISaar Posted October 20, 2010 Report Share Posted October 20, 2010 yep, happens with the wifemobile all the time... the only time it doesn't happen is right after a cold start and the alt is pushing out more voltage. the instrument cluster and HVAC controls will usually dim as well if you're watching them. i've also considered LED brake lights, but considering i have a large section of brake lens missing, that's been put on hold. Quote Link to comment Share on other sites More sharing options...
Regal_GS_1989 Posted October 20, 2010 Report Share Posted October 20, 2010 Its' not just GP's. My Mom's lumina does this too, as well as when the ABS cuts in. My regal does this as well, just not as noticeable. Quote Link to comment Share on other sites More sharing options...
Schurkey Posted October 22, 2010 Report Share Posted October 22, 2010 Welcome to "engine slows down, alternator voltage is reduced". If this were me, I'd be getting the battery and alternator tested. A weak battery, a dying alternator, or corroded wiring could each cause the headlights to dim when you take your foot off the gas to apply the brake. Quote Link to comment Share on other sites More sharing options...
96grandprix Posted October 22, 2010 Author Report Share Posted October 22, 2010 (edited) Welcome to "engine slows down, alternator voltage is reduced". If this were me, I'd be getting the battery and alternator tested. A weak battery, a dying alternator, or corroded wiring could each cause the headlights to dim when you take your foot off the gas to apply the brake. the 96 g.p. has 6 brake lites. think about that , most cars only have 2. more current flow=way more momentary voltage drop, especially at low rpms,(when alt output is low) when your braking. i think from the posts here that its "normal" for the car to do that. battery is new and alt is good. cranks over fine. Edited April 15, 2014 by 96grandprix Quote Link to comment Share on other sites More sharing options...
jeremy Posted October 22, 2010 Report Share Posted October 22, 2010 the 96 g.p. has 6 brake lites. think about that , most cars only have 2. more current flow=way more momentary voltage drop, especially at low rpms,(when alt output is low) when your braking. i think from the posts here that its "normal" for the car to do that. battery is new and alt is good. cranks over fine. but ill gaurandamtee u that when i put led brake lites in, the problem will b gone. i wouldn't say it's "normal".....i know none of my old grand prixs had this issue Quote Link to comment Share on other sites More sharing options...
Garrett Powered Posted October 22, 2010 Report Share Posted October 22, 2010 you likely need to upgrade your block-to-battery tray ground strap. Quote Link to comment Share on other sites More sharing options...
GP1138 Posted October 22, 2010 Report Share Posted October 22, 2010 the 96 g.p. has 6 brake lites. think about that , most cars only have 2. more current flow=way more momentary voltage drop, especially at low rpms,(when alt output is low) when your braking. i think from the posts here that its "normal" for the car to do that. battery is new and alt is good. cranks over fine. but ill gaurandamtee u that when i put led brake lites in, the problem will b gone. ... and you'll still have the problem causing the dimming lights. Your alternator might be going bad, or a ground might be bad. I had this problem when my alt was weak, and also when my battery cables were slightly loose. I don't have this problem now. Quote Link to comment Share on other sites More sharing options...
visitor Posted October 23, 2010 Report Share Posted October 23, 2010 The fact that it has 6 lights in the brakes is NOT the cause for your dimming. follow the suggestions in this thread Quote Link to comment Share on other sites More sharing options...
Crazy K Posted October 23, 2010 Report Share Posted October 23, 2010 my 92 Lumina had a worn out alternator. it would do the dimming issue described. It was putting out 12 volts but only 5 to 10 amps (100-105 rated?) when I realized there was a problem... the bad alt was also making alot of alternator whine that could be heard through the radio... I have been converting my third brakelight to LED on my cars, as they are usually halogen bulbs and probably draw more current than the rest of the lights.... Quote Link to comment Share on other sites More sharing options...
zrothauser Posted October 23, 2010 Report Share Posted October 23, 2010 I was having this same problem the past few months. Then last week my battery died, and since replacing the battery I have not had the problem. Quote Link to comment Share on other sites More sharing options...
Night Fury Posted October 23, 2010 Report Share Posted October 23, 2010 It may happen to a lot of the cars, but it is not 'normal' and is not supposed to happen. My 91 doesn't do it at all. Quote Link to comment Share on other sites More sharing options...
mra32 Posted October 24, 2010 Report Share Posted October 24, 2010 I have been converting my third brakelight to LED on my cars, as they are usually halogen bulbs and probably draw more current than the rest of the lights.... Not to mention its probably just as expensive! I replaced mine and was amazed at the $10 price. I also LOLd at the fact that it was billed as a foglight bulb Quote Link to comment Share on other sites More sharing options...
spiderw31 Posted October 25, 2010 Report Share Posted October 25, 2010 (edited) If what you're seeing is a really fast dim, and then the lights recover, clean solid connections will help but I doubt eliminate the problem. I've had that issue on many cars I've owned, across manufacturers. It is caused by inrush current. When you close the circuit, there is a very brief but substantial surge in current draw before it reaches steady state current draw. The more bulbs (greater load) the greater the spike caused by inrush will be. Also the more load already presented to your charging system (i.e. your headlights) the more noticeable the effect will be. I see it on my GP with the brakes, and I see a much more noticeable dip when either fan kicks in. In both cases though, the voltage almost immediately recovers. I even see this on my Legacy GT when the A/C kicks on at speed. Short answer though: If the dimming really is just for a split second and the voltage and brightness recovers fully, thats normal. Edit: And BTW, I have a new alt and batt on the GP, and all contacts are clean, shiny and tight. Edited October 25, 2010 by spiderw31 Quote Link to comment Share on other sites More sharing options...
Night Fury Posted October 25, 2010 Report Share Posted October 25, 2010 Then why doesn't it happen on mine? Quote Link to comment Share on other sites More sharing options...
GTP091 Posted October 25, 2010 Report Share Posted October 25, 2010 I've had this on my old 83' cougar and long ago on my GTP. It's caused by bad connections like many have already said. Clean your connections. And not just the easy lazy spots; the alt, engine ground, chassis grounds etc. I cleaned and resealed almost all of the connections on my GTP over the years and the problem went away. Now I have LED on it, but if you put them in to cover the issue they will fail quickly. LEDs don't like voltage drops below their recommended range. Quote Link to comment Share on other sites More sharing options...
spiderw31 Posted October 25, 2010 Report Share Posted October 25, 2010 Then why doesn't it happen on mine? The physics of it say that the effect happens all the time. The amount of load, the resistance of the connections (directly related to their cleanliness), and the quality of the voltage regulator all have an effect on how noticeable it is. Alt in good shape, fresh battery, clean connections, and a fast voltage regulator; the drop in voltage may be so brief that you don't see it. It's still there though. Quote Link to comment Share on other sites More sharing options...
white4d96 Posted October 31, 2010 Report Share Posted October 31, 2010 It's weird on mine because when I use the brakes, it does that 'fast dim' like was mentioned before, but if I turn my hazards on, it stays dim while the hazards lights are illuminated. Then again my batt is total dog shit too, I found out the other day... Quote Link to comment Share on other sites More sharing options...
gp1991 Posted December 4, 2010 Report Share Posted December 4, 2010 mine does it sometimes for a split second when i brake Quote Link to comment Share on other sites More sharing options...
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