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Headlamp Electrical Problem

Discussion in 'Technical Discussion' started by Njg425, May 18, 2017.

  1. Njg425

    Njg425 Member

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    Hey everyone, thanks in advance for your help. I have scoured this site and others and haven't been able to find anything that helps. My headlights suddenly quit working. The relay is good, as are the fuses, and I have voltage at the low beam fuses. The bulbs are good, I even swapped one with an extra I have. However, I have voltage on BOTH sides of the fuses, and no voltage at either plug. Makes me think there is a short within the fuse box somewhere. Do you guys have any ideas I could try before tearing out the fuse box? Thanks again.
     
  2. Blckshdw

    Blckshdw Moderator

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    If you had a short, the fuse would pop. It's more likely that you have an 'open' somewhere. You can unbolt the fuse block from it's mount, and unclip the wiring bundle connectors and check the metal traces underneath for any breaks or cracks. If you find any, you can solder them back together.

    Otherwise, you could be looking at a wiring issue somewhere between the fuse block and the headlights, which would be a bit more tedious to track down.
     
  3. Tiggerr

    Tiggerr Gold Supporter

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    Mine have done that before as well...just quit for no reason... only the low beam though... my highs would still work... I'd thought the relay was good too however it wasn't... did you try swapping it for a known good relay?
     
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  4. budwich

    budwich Well-Known Member

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    you say the relay is "good"... not sure what that means... but is it operating?
     
  5. Mooseman

    Mooseman Moderator

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    Swap it with the fan relay. Same type and lower amperage draw so less likely to fail. While you're there, inspect the connectors for it in the fuse box. There have been instances of melting connectors.
     
    Redbeard likes this.
  6. Mounce

    Mounce Silver Supporter

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    Wouldn't hurt to find the ground for them either. I'd almost assume both sides utilize the same ground.

    Definitely swap the relay with another, though, like mentioned. It's a solid state relay and can act funny, also very very common failure point. If it's bad replace with ACDelco only, lesser relays are known for overheating and melting.
     
  7. Njg425

    Njg425 Member

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    I did swap the relay with the solid state relay for the fan that is right next to it and it still doesn't work. However, I DO have voltage at the fuse, which to me indicates that the relay is working. Mounce, I thought about the ground issue as well but the schematic says that they use two separate grounding points so that seems unlikely. Blckshdw, you're correct in saying there's probably an open not a ground. I just really can't think of a reason why there would be voltage on both sides of the fuses though. Mooseman, I will also try to inspect the connections more closely it was getting dark while I was looking through it. Thanks for the input guys, I really appreciate it. I'll dig into it more this weekend and let you know how it goes.
     
  8. budwich

    budwich Well-Known Member

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    all that you have proved with the "do have voltage at the fuse"... is that you have voltage at the fuse... it has nothing to do with whether the relay has been operated.... that voltage is always there... it is "always on circuit / hot". In normal circuits, the fuse is first and protects the entire circuit there after INCLUDING relay contacts whether they are open or closed. You need to determine if the relay has been operated.
     
  9. Redbeard

    Redbeard Well-Known Member

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    Do yourself a favor. Check to see if there is enough current to illuminate a test light. We can have a multi meter read 12v yet will not illuminate a bulb. Check it all with a test light. And I would suggest NOT a test light that uses a LED bulb either.
     
  10. Njg425

    Njg425 Member

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    So I had thought I had narrowed it down to the headlight switch, so I ordered a new one. I am still waiting for it to arrive, but this morning I noticed when I unlocked my car that the reverse lights also didn't come on when I pushed the unlock button like they normally would. Is there a fuse in the fuse box under the back seat that protects the BCM when it is switching the lights on and off? I couldn't find one. What are your thought on this? Thanks!
     
  11. Njg425

    Njg425 Member

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    Also, forget everything I said about there being voltage at the headlight fuses, I was a tired idiot that first night. I have looked through it all fairly well now and everything seemed to work fine up to the switch but I couldn't think of a way to test it without breaking something by applying 12 volts somewhere that should only see 5V from the BCM.
     
  12. Mooseman

    Mooseman Moderator

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    There probably is a fuse for the BCM but you would have more than just headlight problems if it was that.
     
  13. Njg425

    Njg425 Member

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    There's a fuse protecting the HDM that blew, #53 I believe. I have no idea how that happened. Thanks for all of your help guys. This site is awesome.
     
  14. Mooseman

    Mooseman Moderator

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    Glad you found it. If you found this site useful, would you donate a buck or two to the Tip Jar? Anything would be appreciated and it all goes to help keep the site up. Thanks!
     

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