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Got a quick headlight question.

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Old Jul 8, 2009 | 12:45 AM
  #1  
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Default Got a quick headlight question.

I have a '97 C5 and have noticed lately that the headlights seem to dim a bit and then go back to normal. They do this off and on while I drive.

I thought about replacing the alternator with a High Output version but would rather put my mod money toward a new HID Light Canon Set Up.

Should I replace the alternator. Do you think its bad or going out?

Since the HID Bulbs are less wattage is it reasonable to assume if I installed them they wouldnt dim off and on?

Please help....
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Old Jul 8, 2009 | 12:26 PM
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Could be a couple of things. Check your connections to the battery. Make sure they are free of corrosion.

I'm thinking the dimming for a second is from the cooling fan(s) coming on. These will put a brief load on the electrical system that cause the lights to dim for a second. How bad is the dimming?
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Old Jul 9, 2009 | 12:00 AM
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Its pretty noticeable. Almost as if I am doing it on purpose.

My battery is an Optima Red Top thats brand new and all tight and perfect.

I think you may be on to something though about the fan. My local shop suggested I not change the thermostat and instead change the temp for the fan to come on. I guess its supposed to accomplish the same thing.

I wonder if I bought some high performance alternator my problems would be all gone.
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Old Jul 9, 2009 | 02:48 AM
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Maybe your new HID bulbs are more susceptible to surges in the electrical system than the older OEM's? Due to the fact that the HID's are higher intensity, maybe they are more sensitive to irregular voltage surges. If you are driving 55 or more should your cooling fans come on? Maybe you are getting some surges when your A/C comes on too? You should definitely check out the alternator if it is original for sure. Let us know what you find out, I'm just "thinking out loud", hope we can help you.
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Old Jul 9, 2009 | 11:55 PM
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Thanks guys. I dont have the HID set up yet. I have the stock C5 headlights and bulbs. I am debating on getting the "Radioflyer" light cannon set up. But its on hold since I want to try and figure this out first. It would be even more embarrassing to have upgraded to a very slick HID set up only to have it flicker and dim.
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Old Jul 10, 2009 | 01:53 AM
  #6  
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Before you do anything, consider a "Big 3" wiring upgrade. You can google it for all kinds of info. The upgrade uses bigger wire either gauge 0/1 or gauge 4 (that is up to you) and you run a positive wire to the alt, chassis ground to block and chassis ground to battery negative. Audiophiles do this all the time to eliminate dimming lights.
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Old Jan 6, 2010 | 08:24 AM
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ITSQUIK, did you ever figure this out?

Reason I am asking, and bumping your thread, is becasue I noticed my head lights dimmed a couple times on my way to work on my 03 AE. I have about a 15 - 20 minute drive and stock headlights. Checked my volts and I was at 14.0, and had the heater on. Battery is good, just checked it last week.
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Old Feb 1, 2010 | 11:48 AM
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My lights dim like this too. I have a new battery and it still happens. I worry other drivers will think I am flashing them to move. I never thought it would be the cooling fans. I will have to watch them to see if it is.
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Old Feb 1, 2010 | 12:00 PM
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Originally Posted by VinnyT
Could be a couple of things. Check your connections to the battery. Make sure they are free of corrosion.


I'm thinking the dimming for a second is from the cooling fan(s) coming on. These will put a brief load on the electrical system that cause the lights to dim for a second. How bad is the dimming?
I had a similar problem; headlights and panel lights would dim when the cooling fans or the AC came on. Thought my connections were tight when in fact, the new battery had shorter thread depth than the original factory Delco battery. Read about the problem with others here on the forum and took their suggestions and put a couple of copper washers on the battery cable bolts then tightened them down and the problem went away. You might check that.
Also make sure your connections at the starter are tight; that is a common place for loose connections/corrosion also.
Let us know.
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Old Feb 1, 2010 | 02:26 PM
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I've had this for years and I've read on here that the dimming headlights thing is 'normal' for our cars. I wouldn't worry about it too much.
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Old Feb 10, 2010 | 08:50 AM
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It was driving me crazy!! I ended up buying a very expensive highend alternator and the problem went away. I will try and find the name of the company and post it up.
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Old Jul 17, 2011 | 12:49 PM
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Would the brake lights coming on affect the lights too?
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