Dimming lights.... [Archive] - GrandAmGT.com Forum


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02-10-2005, 12:41 PM
Not too long ago I had my alternator replaced b/c it went out. Ever since, the lights dim out when I press on the brake pedal. Not for long though. They dim out for about a second and then kick back to normal.
I took it to Autozone so they could run a test on the battery since the mechanic never charged the battery when he replaced the alternator. He just let the alternator charge the battery. Anyways, Autozone said it looked like the battery can't hold extra loads very well. So when I press on the brakes for example, all other lights (interior and exterior) dim out until the alternator picks up the extra load.

My question is, does this sound right to you guys? I always thought the alternator handles all of the electrical power of the car while it's running. I had no idea that the battery had anything to do with extra loads.
Should I just have the battery replaced?

I apologize for sounding like such a nerd, but I would rather get an opinion from people who know.

02-10-2005, 01:42 PM
My 96GAGT has done that since day one, But in my case it happens when I am comming to a stop and I depress the clutch. The lights dim for an instant and then return to normal intensity. I have had the car since 1996 and have 120,000 miles on it. It still does it even after a new battery and a heavy duty alternator, there dosen't seem to be any other problems associated with the dimming lights. I talked to the mechanics at the dealership where I sold Pontiacs and they all told me it was nothing to worry about.
A lot of the electrical equipment is directly related to the battery for operation so there is a load on the battery. When the car is running the battery and alt. work together to keep things operational. My alternator went when I was about 35 miles from home and it was getting dark, I just made it home before the car died. The next morning I tried to drive to the garage [about 3 miles away] I jumped the car and was able to drive about 1/4 mile before the car died again, with all electrical equip. turned off the fuel pump would quit and then the car was DOA. Had to have it towed, so I guess a lot of stuff is tied right to the battery. As for your lights mine have been doing it for a long time I would get it looked at if I noticed it getting worse. Hope this helps.


02-10-2005, 01:49 PM
Thank you for the info.
Mine only started doing after the new alt was installed. And that was about 3 months ago. At first it was bad, then little by little it got better. Now it's just a consistent slight dim.
Nothing major, but it bugs the hell out of me, ya know?
I wonder how it would affect the lights if I were to put a system in the car?

Mike Jung
02-10-2005, 02:04 PM
1st: ALWAYS fully re-charge the car battery when geting an alternator changed.
& why didn't the place that changed your alternator run a "A.V.R. electrical system test" ?

If the battery is no-good or weak; you WILL eventually kill the new alternator prematurely.
Because the best way to kill an alternator is by using the alternator to charge a dead/low battery.

If Autozone says your battery does not have much capacity left -> GET A NEW BATTERY!
Especially, if this is your stock OEM AC Delco original bettery...it is about that time that they start dieing.
My AC Delco died on me in 3-years; but started showing signs of going in 2-years.

& yes the battery provides the electrical power when the car is like at idle (when the alternator is not spinning too fast) & you have more electrical demand then the alternator can provide.

Especially, in the hot summer with the AC on in stopped traffic during rush hour in stop & go environment.
Example: In the summer heat with AC on, in stuck traffic when it is raining hard (so the wipers are on) & your full headlight & fog lights are also on.
At lot of people kill their batteries in the summer heat while running their AC on in stopped traffic.

02-10-2005, 02:22 PM
Well, you do need a new battery. The stock one is only good for 5 years.

As for the lights dimming, it's normal. Happens to my car and I have an Optima Red Top. Happens to thousands of other GA owners as well.

02-10-2005, 02:23 PM
You would have thought the mechanic would have charged the battery, but come to find out, he didn't.
I don't have the stock battery in it. When I got the car last year, it had an aftermarket battery already. The dealership couldn't give me any info on when that was purchased.

I'll be going out later today to buy another battery.

Thank you for the advice.

02-10-2005, 02:25 PM
Well, you do need a new battery. The stock one is only good for 5 years.

As for the lights dimming, it's normal. Happens to my car and I have an Optima Red Top. Happens to thousands of other GA owners as well.

When I got the car, it already had an aftermarket battery in it.
I'm just gonna go out later today and get another one.

That sucks with the lights dimming. Now it's gonna annoy the hell out of me even more everytime I press on the brakes.

02-10-2005, 02:31 PM
Well, for future reference, ask to get your battery recharged before the new alternator is used.

As for the dimming lights, people have gotten larger alternators and fixed the problem. So, if you are wanting to spend some more money, there is a fix.