Headlights dim 07 Cobalt LS

angellscobalt07

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Hi there, newbie here. I have a 07 Chevy Cobalt LS that I've been trying to fix up myself. One of the issues I've been having is the headlights will dim and fluctuate in intensity when they're on, noticeable at night. They would dim at the same pace of the dashboard which seemed to be in time with listening to the engine.

I replaced the battery, serpentine belt and alternator, in that order. Maybe about a week apart from each other. Anyway, I was dreading and putting off replacing the alternator because of how difficult it was to get to but after the last two attempts with replacing the 10 year old battery and super worn out belt, the alternator seemed it was going to be problem solver (after reading it was most likely the culprit on numerous forums/websites).

After tearing up my arms reaching in and cursing all morning, I was able to get the alternator replaced. Drives fine, arguably feels like it drives with a little more pep but maybe that's in my head.

Come nighttime, I could fully test to see if my issue was gone. At first glance, the lights were consistently brighter and the dash no longer dims at all. As I sat there and looked closely, I turned the heater on full blast and noticed the headlight intensity changed subtly. I drove the car around the block a few times to see if I'd notice it on the road and if maybe the new alternator needed a quick drive before doing its thing properly. I don't notice it much while driving since it was so embarrisingly obvious before. I pulled back into the driveway and stared at the wall being hit with headlights some more and that's when I noticed it was still dimming ever so slightly. The intervals at which it dimmed is much longer now, say 3-5 seconds. And the dim is very subtle, but I know it's there and my fear is that it'll get worse over time again like when I noticed it for the first time about a year or so ago.

Can anyone point me in the direction of my next step should be? Will it go away in a couple days with the new alternator? I made sure connections to the alternator and battery were solid and snug.
 

zora

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Rather than throwing parts at the problem have you ever used a voltmeter to check alternator output and battery charge?
 

zora

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What is it doing when you have the headlight issue?
12.3 is not a fully charged battery.
14.5 is on the high end of charging.
Have you carefully looked at the battery cable terminals where the cable connects?
They can develop corrosion and cause a poor connection.
Also check the battery chassis ground and starter connection.
 
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jnde207

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Sounds like a bad ground connection but chasing an electrical problem is ALWAYS a pain in the butt.
I replaced a bad battery and alternator because of whining in my speakers with the system turned off, it went away but now I'm starting to hear it faintly coming back.
All in all I own a 2011 Chevy equinox LS 2.4L so I have just accepted the fact that it is what it is, lol....
 
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