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no back up lights

Discussion in 'GM Electrical Tech' started by freddie, Apr 23, 2012.

  1. freddie

    freddie New Member

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    On my 03 Avalanche one of my back up lights stopped working. So i bought new bulbs. The old bulbs didnt look blown so i tried them in the tail lights and they worked. I checked all the fuses and they were good. Also when i changed the bulbs i changed both sides and now neither one will work. Some how i did get them both to come back on for a little while when i was testing the socket with a test light. Some one told me to look at the circuit board but i really dont know what do with it. Why do we even have a circuit board? How do i tell if the board is bad andhow bad is it to change out? If anyone knows anything about this please help. Thanks.
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  2. Enkeiavalanche

    Enkeiavalanche Moderator

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    This is the factory lights right? Check the socket. Alot of Avalanche owners have had problems with them coroding. Are you the first owner?
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  3. freddie

    freddie New Member

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    I am the second owner. The sockets appear to be in good shape. Anderson yes it is factory.
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  4. Enkeiavalanche

    Enkeiavalanche Moderator

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    And you said with the Test light it works fine?
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  5. freddie

    freddie New Member

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    Tested the test light ong the battery before and after to make sure ot works
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  6. Enkeiavalanche

    Enkeiavalanche Moderator

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    Did you test the leads by the socket? (the wires)
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  7. moogvo

    moogvo Moderator

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    try to flex the circuit board a little while they are on. See if they intermittently come on and go off. If they do, the board has either a broken trace or a cold solder joint.
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  8. freddie

    freddie New Member

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    I tested just the inside of both of the sockets. I was kinda short on time. It will be thursday or friday before i gwt to work on it again. Just wanted today seee what else i need to check. Sorry for the misspelled words my mobile web wont let me fix them for some reason.reading
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  9. RayVoy

    RayVoy Active Member

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    So, let's not get this problem overly complicated.

    Before you took it apart, you had one side working, one side not working..........................probably a bulb.

    You took both side apart and now neither side works...............probably using the wrong bulbs, or a blown fuse.
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  10. moogvo

    moogvo Moderator

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    Don't ya HATE when that happens?! I even have that problem on my iPad... It decides to alter words I type in. (that's why every single one of the posts I make from my phone or pad have been edited)
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  11. freddie

    freddie New Member

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    Yeah sometimes i hate this thing. The bulbs are all correct sizes in working condition. The fuses are also
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  12. moogvo

    moogvo Moderator

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    Pound on the lenses (with your open hand) and see if they flicker on and off.
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  13. Strino78

    Strino78 New Member

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    In its plainest electrical form; It sounds like you have a ground issue. When you remove the bulbs, test the socket.. etc.. the wiring harness is being moved and tugged on to some degree, potentially creating or eliminating grounding issue.
    You do not have any blown fuses, and the bulbs that were removed were tested to be good. That's another clear indicator of a ground short. If you have brake lights, then a ground is your culprit. Check your frame grounds by your rear bumper/frame by the spare tire.



    If they salt the roads in SC when it snows, that's the likely culprit... that and time. :D
    Last edited: Apr 23, 2012
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  14. freddie

    freddie New Member

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    They do salt the roads only about once or twice a year but they do. I will defiantly look at the ground also.

    ---------- Post added at 08:28 PM ---------- Previous post was at 06:50 PM ----------

    I did get a chance to go outside and check a few things before the sun went down with no luck though. I check the ground and it appears to be fine. It looks as though there is only one ground for the whole rear lights. I followed all the wires to the lights back to the circuit board and only found the one ground. So if the ground was bad then none of the rear lights would work. I look some more at the sockets on both back up lights sockets and they looked clean and in good shape. I even put the test light on the back up connection on my trailer hook up. I shook and tapped on the circuit board and nothing happened. I tried to pull off the one of the connections on the circuit board to look at them but it felt like i would break it. So that will have to wait till i have more time.
    #14
  15. Enkeiavalanche

    Enkeiavalanche Moderator

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    With the Test probe Probe the Wires going to the Back up light socket..
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  16. Strino78

    Strino78 New Member

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    Salt spray is a killer to all things metal. I live in Northern Ontario, and get my fair share of it too.

    Try removing the ground, and giving it a good cleaning with some sandpaper on the connector and frame. They can build up corrosion between the ground and frame, and it will look good to the naked eye. Your ground setup sounds to be the same as what is on my '94 K1500. Do your brake lights work? Even with a bad ground the brakes lights should be the only lights in the rear that keep working. I had this exact problem a year ago, and got stopped by a state trooper late at night on the I-75. I was unaware of it...as I had lights when I started my trip earlier that night. He was real nice and let me go with "Are you comfortable riding your brakes so you can be seen from behind? It'll get you home."

    Sure enough.. the ground was there, it just wasn't good.


    The trick I figured out is with your parking lights on -- remove one of the license plate bumper lights and leave it connected in the socket. While you're under the truck tinkering with the ground; you'll be able to see the bumper light when it comes and know you have a nice solid connection. Put a little bit of white grease, di-electric or anti-sieze compound over it -- and you'll be good for a while.
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  17. freddie

    freddie New Member

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    I think that the ground was the problem. I am going to give some time to see for sure though. Thanks guy for all of your help!
    #17

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