Question about Cadillac STS

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Brake lights/turn signals don't work when headlights on

When it's night & the headlights come on, my brake lights come on but won't brighten when I brake and the turn signals won't blink. They work fine when the headlights are off. Obviously, this is a major hazard. What's the problem & any solutions?

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  • moblind Nov 12, 2008

    The blinkers do come on, but they won't blink. Again, this only happens when headlights are on. During daylight, everything works as it should.

  • moblind Nov 12, 2008

    FYI - this is a 1996 Cadillac Seville STS

  • donnyplato Jan 22, 2009

    I'm having the same problem on my 2002 honda civc si, I have been trying to figure it out for the last two hours. I checked the wires, dual pole bulbs, all the plugs, all the fuses looked god, everything looks good but still cant find the solution. Please someone HELP


  • Anonymous Mar 31, 2014

    Turn signal light comes on when headlights are on then wont blink but works fine when lights are off

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Its more than likely a bad grounding wire in the tail lights

Posted on Feb 04, 2010

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Its probably a bad alternator check it and make sure its workin right if its not that then it could be the voltage regulator do the blinkers come on but not blink

Posted on Nov 12, 2008

  • Walter Morris Nov 13, 2008

    ok i think it is definately an alternator problem because the way the flasher works for the blinker is when current flows through it and illuminates the bulbs it heats up a small strip of metal inside the flasher and causes it to break connection and the lights go out untill it cools and then the strip of metal falls back to its original position and the lights come back on if the flasher doesnt get enough power the lights will just stay on cause there isnt enough current to heat up that strip. so apparently your alternator isnt producing enough current to run everything

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Hello moblind, you might look into the fuses, it sounds like one of them is blown,..
or a bad connection somewhere.

i look forward to your posts

Posted on Nov 12, 2008

  • Eeeeeeeeeekz Nov 13, 2008

    see if you can get a hold of a diagnostics tester (at like a autozone or something like that) there is probably a error code that you just haven't noticed.

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