71 Duster Headlight issues

Discussion in 'Electrical and Ignition' started by Racinjason, Jul 6, 2018.

  1. Racinjason

    Racinjason Member

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    Own a 71 Duster 340 car. After driving for about 20 minuets the headlights start to flicker. They go on and completely off. Park it let it cool and the lights work fine for another 20 min or so. Any suggestions
     
  2. Alaskan_TA

    Alaskan_TA Well-Known Member

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    It may be the high beam dimmer switch.
     
  3. Racinjason

    Racinjason Member

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    Ok do you know, does the low beam circuit go through that switch as well?
     
  4. Jimacuda

    Jimacuda Well-Known Member

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    yes.
    inexpensive part and easy to replace.
    check the connections on the floor switch.
    check the harness ground wire connections for the headlights as well.
     
  5. Racinjason

    Racinjason Member

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    Ok thanks fellas I’ll try that
     
  6. Alaskan_TA

    Alaskan_TA Well-Known Member

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    Corrosion can affect the function & it is prone to water damage if it ever got wet from a wiper pivot seal leak or from another issue.
     
  7. 67Dart273

    67Dart273 Well-Known Member

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    The headlight switch has a breaker built in. Does this happen on both high and low beam?

    Bad connections at the headlight connector
    Bad/ going bad switch breaker
    Bad connections at the dimmer switch
    Bad connections at the firewall connector (one beam only)
    And of course the ground normally out at the rad support

    Frankly, since this seems to repeat, I'd go for a bad breaker of bad connection at the switch which causes heating of the breaker
     
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    • Racinjason

      Racinjason Member

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      Yes it will do it both on high and low beam. Usually on high beam it starts screwing up sooner. I definitely think it something heating up. Look at and cleaned the firewall connection not that it needed it. I’m thinking either high/low beam switch or the headlight on off switch especially if it has some sort of breaker or relay built into it.
       
    • crackedback

      crackedback FABO Gold Member FABO Gold Member

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      You have an area in the system with high resistance. If the lights are shutting off, it's likely tripping the breaker inside you headlight switch.

      The factory wiring has a lot of voltage drop with long runs and many connections. One solution for improved lighting is a relay kit like I build for our mopars. The light performance will improve a lot and it hides pretty easily in the factory wire runs.
       
    • Mattax

      Mattax Just the facts, ma'am FABO Gold Member

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      The 15 amp breaker is inside the headlight switch.
      The headlight circuit is the longest and weakest. Chrysler used the minimum wire & terminal sizes for the job - 18 gage to the lights, 16 gage to the dimmer switch. Usually its not just one poor connection like a switch, but a the combination of resistances then topped off by one really bad one. That list 67Dart273 covers all of the junctions for the headlight circuit. However, the power comes from the main circuit - and any voltage drops along the way to the headlight switch will also result in the headlights trying to draw more current. (The headlights want power. When voltage drops, they try to get the power by pulling more current). So it is also important that the alternator's output circuit is in good condition, as well as the battery connections.

      In my experience, it is worth checking each connection including at the headlight switch. While doing so look for evidence of oxidation on the copper at the terminals - an oxidized wire will carry less current, as well as evidnce of heating. Then look for chafing of insulation. For a non-concours car that is driven at night, a relay system is well worth it.

      If you want to narrow down the search, remove a lamp and measure the voltage going in. Compare that to the system voltage. System will be battery positive if the engine is off, alternator output if the engine is on. If the voltage at the lamp is more than a few tenths lower than system, there's resistance somewhere(s). If not, then the problem is probably in the ground. An in-betweeen place to check for voltage drops is at the bulkhead connector.
       
    • superchargeddrt

      superchargeddrt FABO Gold Member FABO Gold Member

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      This is usually caused by dirty contacts in the ignition switch. You can install a relay to feed the ignition terminal of the voltage regulator. Check out this diagram, it will help you. Charging system relay modification.jpg
       
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      • Mattax

        Mattax Just the facts, ma'am FABO Gold Member

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        Regarding this ^
        The headlight circuit is hardwired to the main power circuit.
        The ignition switch is not involved other than very indirectly (allowing power to the voltage regulator & alternator field).

        A systematic search will get you closer to the answer better and quicker than internet guesses...

        IMG_7228.JPG

        IMG_7229.JPG
         
        Last edited: Jul 8, 2018
      • philcollins

        philcollins Well-Known Member

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        Change the headlight switch
         
      • superchargeddrt

        superchargeddrt FABO Gold Member FABO Gold Member

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        I guess I didn't read the original post as well as I should have. The headlight switch and bulkhead connector are always suspect. You can put relays on the headlights to lower (just about eliminate) the current on the factory headlight circuit and it will make you headlights much brighter. I did this on mine and it makes a huge difference.