Need a little bit of wiring assistance

Electrical and Ignition

  1. StevieMac

    StevieMac Active Member

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    I have a 70 Duster that is just giving me fits with some of the electrical. Simply put, I am not an electrician and I am trying to figure this out....

    When I pull the light switch out, I get headlights, but no tail lights or dash lights. If I turn the knob, the dome doesn't come on either. If I press the brakes, the brake lights come on, passenger side dimmer though. If I put it into reverse, no back up lights. Before I take the dash apart, would a lose ground wire in the trunk be causing all of this? I'm looking for the ground on the tail light assembly, but can't find hour it. It has to be there somewhere....

    Any advice is greatly appreciated
     
  2. krazykuda

    krazykuda Well-Known Member FABO Gold Member How-To Section Editor

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    Have you checked all of the fuses in the fuse block under the dash to the left of the steering wheel???
     
  3. krazykuda

    krazykuda Well-Known Member FABO Gold Member How-To Section Editor

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    Taking the grounds apart and wire brushing them will ensure that they are getting a good connection would be a good start...

    Do you have a test light and continuity tester??? Those are valuable tools for checking wiring and diagnosing problems....
     
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    • Dana67Dart

      Dana67Dart Like a fine wine, only getting better with age! FABO Gold Member

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      • Have to ask... you have checked all bulbs in question for function and type?
      • Did things ever work correcrly?
      • If yes what changed from thentering to now?
      • Backup lights use a switch on column or console, switch could be bad.
      • Brake lights use switch that pedal pushes on, seems to be working, one side dimmer than other does suggest ground or bad connection.
      • Head lights but no tail lights or dash lights suggests headlight switch.
      • You didn't talk about turn signal, working ok? Some circuts run through the turn signal switch and /or blinker, and /or flasher.
      • Are your flashers working?

      You can download your Factory Service Manual and wiring diagram from mymopar.com
       
    • 70dart340

      70dart340 Well-Known Member

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      It sounds like the head light switch has failed. Mymopar.com has schematics for most Mopars, they should help you troubleshoot with a good multimeter.
       
    • Mattax

      Mattax Just the facts, ma'am FABO Gold Member

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      Power for headlights comes direct from the main splice. Its marked terminal B1 on the headlight switch. In the switch is a circuit breaker.
      Power for the tail and parking (and instrument?) lights comes from the fuse box and is marked B2 on the headlight switch.
      There's another fuse for instrument and lights after the headlight switch.
      On the 60s cars, the fuse for stop light and dome is the same as the tail and parking lights.
      Your fuse box is labeled. Also should be a picture of it in the operators manual if you have one.
      So check that. If they share it, then its not the fuse since the brake lights work. But if not, that's what the rest has in common.

      Ground connections for the tail - look underneath. Probably one on each side. Probably shares the connection with the reverse and side markers.
      Uneven brightness could be grounds.
      Also could be a loose bulb in socket and other such things. How does that happen. Don't know, but occassionally it does.,
      Also look along the insulation for any place it may have rubbed through causing a short to ground.
       
    • Mattax

      Mattax Just the facts, ma'am FABO Gold Member

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      Basic 60s power connections look like this:
      upload_2019-4-22_9-43-19-png.png
      70 the key switch was moved to the column so there was another connector, and there may be other differences as well. Basic scheme will be similar. Colors will vary.
       
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      • StevieMac

        StevieMac Active Member

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        Thanks everyone. Since I had a extra light switch, and need to add a wiper switch, I went ahead and popped the dash out. Took about 15 minutes... Replaced the switch and before I reinstalled, I thought I would try it. Still no joy. Get headlights, but that is it. Turn signals still work, but that's probably due to them being on a separate circuit. All the fuses are good, as I checked that while I was there. So I guess that I will see what I can find from the back going forward....

        What started all of this was putting 1157, the right size bulb, in the socket. However, it was an led as that is what they wife bought when I sent her to the store to get them.

        But still no side markers, tail lights (other than brake) and no backup lights...

        Thanks for all of the suggestions!!!
         
      • RedFish

        RedFish Well-Known Member

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        Most of our light fixtures do not have actual ground wire. Those mounted in plastic grilles have a ground wire. For all others...The base of the bulb against interior of socket, the socket to fixture, and fixture to car body. That's the ground path. Rust inside the socket can cause no light or weak light as can any weak metal to metal connection.
        Hope you checked fuses with test lamp or meter 'cause just looking at them doesn't always work. Sometimes the link is broken underneath the metal cap on glass tube where we can't see it. Then the clips in fuse box are sometimes so rusted that continuity doesn't happen.
        The reverse lamps are likely powered by radio fuse ( I would have to go to wiring diagrams to confirm ). Reverse lamp switch may be the fault. It's screwed into the transmission.
         
      • Dana67Dart

        Dana67Dart Like a fine wine, only getting better with age! FABO Gold Member

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        Many led lights do not provide enough load to make the blinker or flasher operate. First thing i would do is replace that bulb with traditional bulb.
         
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        • 67Dart273

          67Dart273 Well-Known Member

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          PLEASE PAY ATTENTION, already posted above^^ The headlights and the tail lights HAVE SEPARATE POWER SOURCES

          The tail/ park/ instrument lamps come from a fuse

          The headlights are fed to a separate contact come from the splice in the black ammeter wire

          You need a diagram. Go to MyMopar and download the closes shop manual and the aftermarket diagram. Very first step is to see if the fuse has power

          fuse.jpg

          You can see tail circuit is fuse marked "E". This supplies tail/ park/ instrument and I think cigar lighter. It should be hot at all times.

          After this circuit fuse feeds the instrument lamp dimmer, that power goes through the far right fuse marked inst and feeds all dash lamps with orange wiring. THAT FUSE then is only hot

          1...If the tail fuse is good and working
          2....If the light switch is in "park" or "head"
          3....and the dimmer control twisted somewhat to left
           
          Last edited: May 18, 2019
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          • krazykuda

            krazykuda Well-Known Member FABO Gold Member How-To Section Editor

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            The 70 plymouth service manual is available for free download here:

            MyMopar - Mopar Forums & Information - Service Manuals


            Pay attention to 67Dart273, he knows his sh!t....

             
          • DemonK9

            DemonK9 Well-Known Member

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            x 2 for paying attention to 67Dart273 on any testing/advise he gives!!!!
             
          • Tooljunkie

            Tooljunkie King of cobble/master of the broken bolt FABO Gold Member

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            Glass fuses that appear good may not actually be good at all.
            Visual inspection is not good enough.
            I have a good incandescent test light i use for testing fuses. If you dont own a test light, you are shooting in the dark.

            The fuses also fail within the little end cap,a failure thats difficult to catch unless you know about it.
            And one more thing the fuse holders can corrode and lose contact too.
             
          • krazykuda

            krazykuda Well-Known Member FABO Gold Member How-To Section Editor

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            I test my fuses with a continuity tester probe on each end and listen for the 'beep'....

            Visual inspection is not accurate...
             
          • famous bob

            famous bob mopar misfit FABO Gold Member

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          • Mattax

            Mattax Just the facts, ma'am FABO Gold Member

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            One more clue. Refer to post #7 & 11
            Dome light is connected direct from the fuse box.
            It has multiple return paths (aka ground wires) . One goes to the headlight switch. The others to the door jamb switches. Any one of those switches closing will complete the circuit.
             
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            • Kendog 170

              Kendog 170 Well-Known Member

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              Ditch the LED and put proper bulb in as well. LED's flow voltage one way and maybe affecting other bulbs??
               
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