Headlights burning out.

Discussion in 'General Repair, Maintenance, and Warranty' started by 007CobaltLS, Mar 9, 2013.

  1. 007CobaltLS

    007CobaltLS Member

    All right, so even though it's not a Mazda, maybe I can get some help here.

    My 07 Cobalt has been in my possession for nearly 6 years. Never really any problems...until recently.

    So back when I bought the car, I installed an MTX ThunderLink sub/amp setup (100 watts, all in one type deal).

    In 2011 I upgraded the head unit and speakers all around along with putting in aftermarket projectors and HID's.

    Sometime last summer I swapped out the MTX for a Kenwood amp that puts out 460 watts and the Boston G5 sub. Not too long after doing that, I had an issue...driver's side HID burnt out. Less than a week later, passenger side burnt out.

    Took out the HID's and put in H7 bulbs (SilverStar Ultra's). Swapped back to the MTX after a few months due to selling the Kenwood/Boston setup.

    Now, I went with a lower wattage amp (200w) and a Polk sub. Installed it all on Thursday morning...Thursday night...driver's side headlight went out.

    I'm sure it can't be coincidence. Any ideas?

    First time it happened I thought maybe moisture got in or something else...didn't really think about the extra draw from the amp.

    Now that it's happened again...I'm guessing it's not moisture.

    Could it be my wiring? The ground possibly?

    The alternator itself? I've heard of overcharging, but never experienced it.



    I'll get the alternator checked out...and the battery (if the problem is the alternator since the battery is only a year old). I'll also double check all my wiring and probably re-do some of it.

    I can't afford to be replacing headlights often so I need to get this figured out sooner than later.

    Last question, if it is the alternator, would you pay ~$150 for a reman? or should I take a chance and spend $30-35 at John's or A-Abco? I know A-Abco has used for $30 that are tested with lifetime warranty.

  2. are you touching the bulb when your installing them?
  3. 007CobaltLS

    007CobaltLS Member

    No, I know better than that.
  4. escort1991

    escort1991 New Member

    Where are your wires all running? Have you checked the grounds?
  5. 007CobaltLS

    007CobaltLS Member

    I haven't had time this weekend, but tomorrow I'm planning on going to have the alternator checked and I'll be cleaning up the wiring.

    What wires are you referring to specifically?

    The Cobalt has the battery in the trunk so all of the wires are short runs for the amp. The only 2 things going to the front are the remote turn on lead and the RCA's to the head unit. I'm going to double ground the amp using the current bolt on the body that I'm using and also the negative terminal on the battery.

    As for headlight wiring...aftermarket projectors, but they use factory wiring harness (since I now removed the HID's).
  6. 007CobaltLS

    007CobaltLS Member

    Update...didn't have time to mess with my wiring. Replaced the burnt out headlight with the cheapest I could find at Wally World...$9.88 for H7 bulbs...

    Then I made sure my ground was secure...it was/is...but I still want to clean it up and make it a double ground running back to the battery negative. I checked to make sure my battery connections were also secure...lots of problems with the OEM battery connectors (they don't always stay tight...found that out the hard way once when my car died and my key was in the ignition...only key...no way to open trunk to get to the battery when key locks in ignition...AAA to the rescue that time.

    Anyway, still need to go through more wiring and clean up my grounds and what not.

    But...I did check the voltage on the battery with car off and the current while the car was running....surprisingly, I was right in my main guess...

    Overcharging...the fucking thing is reading 17 volts while off and just over 20 volts while charging...so the alternator is the culprit...at least I think it is...new cars don't use a voltage regulator like old cars (I mean it can't be rebuilt...just have to replace the whole alternator)...it's in the computer...so my first guess is the alternator...if that's not it, then it's the computer...that would be fun to replace...I believe the BCM is what controls voltage...not sure what that would cost me though.

    I've never seen a battery read so damn high...surprisingly the battery isn't bulging at all. Guessing the battery will be no good though...good thing it's a DieHard Gold...only a year old and it's got a decent replacement period...we'll see if I need to replace it after the alternator is done.

    And yes, I know how to check DC voltage...if I don't know how to use a multimeter, I don't have any business going to school for electronics technology.

    EDIT: Guess a BCM would be about $180-200 shipped from RockAuto...well not the end of the world if it winds up being that, but hopefully it's the alternator only.
    Last edited: Mar 11, 2013

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