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  1. #11

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    Quote Originally Posted by wolfmann View Post
    the only places that i can figure is the flasher unit,
    I think your right. I don't recall the lighting on the rear of your truck, but if you have a different bulb for sig and brake (on each side), it is probably the flasher unit.

    Some trucks (like I said, don"t recall the Silverado), have separated sig and brake circuits (quite sure the Serria is separate, I remember the sigs being amber). One of the jobs of the flasher is to output these two leads into one for the trailer connector.

    Try a new flasher, that will probably solve the problem.
    Ray

    '09 Avalanche LTZ - Black
    '05 Envoy XL (sold)

  2. #12

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    I would suggest before you replace the flasher unit that you take a look at the junction box at the rear of the truck. Sometimes they can get corrosion/moisture. Follow the wiring for your trailer plug (and tail lights, etc.) to a box where all of the harnesses for the rear lights meet and a main harness from the front of the truck goes in. Unplug everything, take the junction box off and make sure everything is OK inside of it. If not, then check your flasher. I had to replace the flasher on my Avalanche due to it making the right side trailer signal work, but not the brake light on that side.

    2008 FORD F350. My new all-around truck.
    2001 Silverado Reg. Cab Not-So-Base -- SOLD
    2003 Avalanche Z71. No Cladding. Check out my Mod thread. - Crashed. Will be rebuilt soon.
    1974 Triumph Spitfire 1500 - Work in Progress
    2003 Sierra 3500 Duramax. The Newer, Better Work Truck -- FOR SALE


  3. #13

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    I'm at work now so I can't get to the truck, but are u referring to the junction on The rear crossmember where the blue harness plugs in and splits to the taillights and markers cause the trailer wiring doesn't connect to it. Or is there another junction that you are talking about??
    Don't Run Your Fingers Over My Truck And I Promise Not To Run My Truck Over Your Fingers!!!

  4. #14

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    Thanks to all I did figure out it was th flasher unit causing the problems. I got lucky napa had them for $29 where everyone else wanted $75!

  5. #15

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    Quote Originally Posted by wolfmann View Post
    Thanks to all I did figure out it was th flasher unit causing the problems. I got lucky napa had them for $29 where everyone else wanted $75!
    Thats a good price. My local Napa here in Canada wanted $135 for one, but I got one at Canadian Tire for $80. BUT, that was for the upgrded LM-487 model that is LED compatible. Either way, $29 is good. I'm glad you got your problem fixed.

  6. #16
    Sr. Engineer
    Join Date
    Oct 2010
    Location
    Indianapolis, In
    Posts
    493

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    Thanks for letting us know what the fix was. I am curious, did the truck lights work OK but just not the trailer?
    2000 GMC YUKON SLT, 5.3L tow pkg, G80 rear/w 3.73 gear

  7. #17

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    The trailer lights did the following right tail light was constant on, the left signal acted like hazard flaahers and right turn signal didn't. Work at all. On the truck every now and then the left turn signal acted like the hazards. But it only did that when cold

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