Lights dim/blink when hitting the break [Archive] - Forum


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01-23-2004, 08:40 PM
For the past few weeks i've noticed that when I hit the break the lights will blink/dim for a sec, the gauge lights, along with the low beams, the lights and everything is pretty much stock, the only thing that can be putting an extra straight on the car is the HU, but theres no other loads on the car. Is this normal? or can the alternator be going bad? its a 99 GASE 3.4L, with about 32k miles.

01-23-2004, 08:52 PM
Just mentioned that it was in the past couple weeks that this started. I happen to live in Michigan, where the past couple weeks has been the big influx of snow for our area. Along with this is a lot more ABS usage. When the ABS system engages, it will add quite a bit of load to the system as it triggers the solenoids and drives the motor pack. As such, you will see a slight dimming for a second or so. Is this what you might be experiencing?

01-23-2004, 08:56 PM
it happens almost everytime i think, the major roads here are dry, lil patches of ice on smaller roads. But i hardly see the ABS light come on.

01-23-2004, 09:04 PM
You wouldnt see the ABS light come on, just possible the low trac light. The ABS light is just a malfunction indicator.

However, if it is all the time, I doubt that the ABS is causing it.

01-23-2004, 09:07 PM
yea thats what i mean, im just tired lol.

01-24-2004, 11:43 PM
I think its pretty normal. Turn of the heat and rear defrost, and I bet it doesn't do it. The rear defrost draws a LOT of power, and when your at low RPMs, you'll experience some dimming. Not a big deal IMO.

01-25-2004, 07:20 AM
If in doubt, just have it checked at a dealership or store. Some stores will do battery and alternator tests for free. You can always upgrade to higher amp alternators and batteries if you desire.

01-25-2004, 09:30 AM
My '99 GT did the same thing until I replaced the battery. Problem gone.

01-25-2004, 09:53 AM
did u replace it with a regular battery? or a performance one?

01-25-2004, 01:42 PM
Mine did the exact same thing and having the rear defrost and fan on made it worse. I had my alternator and battery checked and the battery was a little weak. Instead of having the dealer put another Delco battery in under warranty, I upgraded to an Optima redtop battery and the problem is gone in most situations. I do still notice that when I'm sitting at a stoplight with the rear defrost, lights, brake lights and fan on that there is still some dimming, but thats because the defroster uses so much power. I would say that a high-output alternator would solve it completely, but it's not that big of a deal to me.

01-25-2004, 04:25 PM
today I tried it with pretty much everything off, no heat, no defrost, no headunit, and it still dims. Whats the best way to test battery and alternator?

01-25-2004, 05:07 PM
My 2003 does the same thing, with no loads present. Dealer told me this is normal. I don't believe them but, what else can I do. I checked with Delphi Engineering who makes generators for other product lines (our alternators, at least for 03 and 04 are Bosch BTW). The told me that Delphi alternators have a LRC (load response control) device that prevents this from happening. I have hooked a Tech 2 up while pressing the brakes and I can see the voltage drop from .5 to 2 volts at the instant the brake lights come on, then it immediately returns to normal. I wish I could get a Delphi alt to put on my car to see the difference, but the connection harness is different. Oh, and if I do it with the engine off, there is no problem, it has something to do with the either PCM/BCM or the regulator in the alternator.... just my two cents.


01-25-2004, 05:10 PM
Originally posted by atc3434
I think its pretty normal. Turn of the heat and rear defrost, and I bet it doesn't do it. The rear defrost draws a LOT of power, and when your at low RPMs, you'll experience some dimming. Not a big deal IMO.

*iagree* all those bulbs lighting up, and some power being used by the brakes... You'll get momentary current draw that will cause that if you have a strained electrical system