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.

 

If I remember correctly on my old Cobalt (base) and G5, every now and then it would dim with the a/c clutch kicking in because it's a hard draw on the system, but would go back to normal in 3-5 seconds; which is normal behaviour. I would double check the connections to your headlights and make sure there isn't any corrosion on the pins, and also change out the bulbs (~$20/bulb). Headlight bulbs are #9007