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  • Headlights... no...

    After the unit has sat for a time(overnight), my head lights will come on for a few seconds then go out. They will not come back on when I turn them off and on. the fog and marker lights work fine. blinkers too.

    Something is sinking the voltage. not a direct short to ground but a capacitative type short.

    If I unhook the dimmer switch, I have 12 volts at the red/w post but when I reconnect the sytem it all show 0 around the dimmer circuit. and all other places.
    the dimmer switch function on its own, its not bad. but the bright indicator light does not come on either.

    I have checked every thing I can think of.

    Where do I look next?


  • #2
    Well this is DC (Direct Current not DaimlerChrysler ) so any capacitative short would be insignificant. More likely a poor connection. And it would have the opposite effect by dropping the voltage until the cap is fully charged.

    Any wire, even a 100 gauge wire will indicate a voltage or potential but try to make that wire pass some current and it just wont work. It will quickly drop to 0 volts. The load a volt meter puts on a circuit could be somethink like 0.0000012 amps were as a headlight will draw 20.00000 amps a difference of 16,666,666.

    The plug may be loose on the headlight switch or overheating the plug may of expanded the connection allowing it to heat more causing a worse connection. Crimps may have over heated, corroded, broken. Internal contacts may be bad. Wire strands may be broken. Your problem seems to be between and/or the headlight switch and the dimmer switch.

    Connect all the components (plugs, etc) back together and turn the lights ON.
    See were the wire going to the headlight comes out of the plug?
    Connect your volt meter at this point. If your reading 12 volts here then the problem is at the plug on the dimmer switch. If your NOT getting 12 volts here then the problem is at this connection or inside the switch.

    These contacts can be pushed out to inspect them. Usually their is a little tab that has to be depressed inside the socket. A thin screw driver can do this while pulling on the connector.

    I used a tweeser here:

    You can then try to re-crimp the connector or soldering it, that works for a few days, Or best get a new connector and crimp AND solder it back together.

    A lot of this can be caused by high output lights drawing to much current. That why we always recommend using relays in headlight circuits.
    Last edited by John Strenk; 05-11-2006, 04:57 AM.


    • #3
      man...'s difficult to add anything to one of John's posts, Big D, but I did think of one more thing. Check the connector that plugs into the dimmer switch the same way that John has recommended that you check the others. (His tweezer trick..) I just had one of the tabs back out of the connector far enough not to make a solid connection all the time. It was on one of my marker lights. It would work for two or three days and go out.

      You'd think a poor connection at headlight amp draw would show up pretty quick through some smoke or at least some 'visual curdling' of wire insulation but a Jeep is strange animal at times. Anyway, your mention of the bright light indication not working pointed me toward the dimmer switch. Of course, as you know, electrical diagnosis can be a bear sometimes and each individual will approach these problems with his own theories at work. It's the 'nature of the electron beast'.

      P.S. have you installed a new or another harness?


      • #4
        bone stock, less computer

        Thanks John. Your always up fornt with good info.

        Blackwater- I put the old harness back in minus the emissions computer crap that was not working anyway.

        I will ohm out some wires today and replace 1 ground wire that has a little resistance to it. We'll get it figured out.

        Sometimes I forget this project is FUN.

        Yah, that why I do this...




        • #5

          Bad dimmer switch connection. very intermittent, internal to the switch there was corrosion. She works now .

          Thanks again.



          • #6
            Yes, those rivots can make poor connectiion after some time. Glad you got it fixed.


            • #7
              HeadLights no

              I usaully hang out on the XJ forum. I had a similar problem with my XJ.
              The headlights would just go out. All other lights would work ie dash,turn park
              and brake. Checked the dimmer switch mounted on the ignition. A wire was
              shorted. The wire terminal melted. I replaced the terminal on that wire and problem was solved.