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Electrical Problem with rear lights

Discussion in 'The Garage' started by gumneck, Jun 28, 2006.

  1. gumneck

    gumneck Registered Member

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    Having trouble with the backup lights coming on when I put on the brakes and when I use the right turn signal. All else is fine. I've clean the grounds to the rear lights,cleaned the bulb contacts and tried new ones, looked over the wiring from the firewall to the back lights, eliminated the towing harness with same results, and have jiggled more wires than I care to anymore.

    Any one encounter this?
    Tks Tom

    91 Blazer
     
  2. mike n

    mike n 1/2 ton status

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    You have a ground issue.
     
  3. chevy wrangler

    chevy wrangler 1/2 ton status

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    my 1979 has no back up lights, it has a sm465. is it suppose 2 have them???when i put it in reverse the 4wheel lock light on my cluster lights up, its crazy
     
  4. gumneck

    gumneck Registered Member

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    Tks Mike for the help. Do you suspect the ground issue is where the ground wire at each rear light is attached to the body of the truck at the taillight recessed area? Or is their another ground wire I'm missing?
     
  5. goldwing2000

    goldwing2000 Guest

    Yes, you're supposed to have them. Sounds like somebody switched the wires from the 4x4 switch on the t-case and the reverse switch on the tranny.
    You should check to see if your reverse lights come on when you put it in 4WD!

    gumneck: you need to check both the grounds from each socket to the body and the ground between the body and frame. Use an ohm meter, if you have one. You should have less than .5 ohm between the socket ground and the battery.
     
  6. gumneck

    gumneck Registered Member

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    Tks GW. I'll look again tonight.
     
  7. mike n

    mike n 1/2 ton status

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    Goldwing beat me to it. Follow his advice and it should solve your problem.
    If you have to, jumper the ground from the left taillight to the right side. There's nothing wrong with having too many grounds.
     
  8. goldwing2000

    goldwing2000 Guest

    Werd! :thumb:
     
  9. gumneck

    gumneck Registered Member

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    Well,

    Maybe this will help someone else out. After adding a ground jumper to the rear lights I still had the same problem. After checking each light socket with an ohms meter I found no resistance. Disconnected the left side wire harness socket and still had the same problem. I was thinking then there was a problem somewhere else. At the point of giving up(giving in and paying auto electric shop)by then. I noticed the right side harness connector was real tight to the frame where it goes into the light recess on the body and thought it strange that I couldn't remove it from the clip to the frame. I was about to remove three tailgate hinge bolts to see why I couldn't move the wires. But I said forget it I'm tired of messing with it.

    So this a.m. I took it in and told the guy everything I did, he then did the same routine I did. After cutting a wire in two to eliminate the green wire running to the back it did the same thing. At this point I told the guy about the wire being so tight to the clip I found last night. Here's what I didn't do that he did. Unplug the right side wire harness connector. In doing this , the left side back up light didn't come on when pressing the brakes. This meant the problem had to be in the right side. After telling him about the wires being impossible to pull out of the frame clip, he looked at it and he noticed that the tailgate hinge was on top of the wires to the right rear lights. WHY WOULD SOMEONE RUN A LIGHT HARNESS UNDER THE HINGE???? Pulled the harness out plugged it back in ...working properly. Strange that it started now to act up being that I've had it for about four years.
    I just didn't see it last night and he did. So I'm $54 lighter on that one. I've been fixing this kind of stuff since I've had this Blazer. I'l get it all ironed out eventually.
    Anyway I learned a lessone. Tks for the help.

    Tom
     

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