Neutral safety switch harness question specific to 1974

Electrical and Ignition

  1. DusterDaddy

    DusterDaddy sledgehammer mechanic FABO Gold Member

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    Hello,
    I am rebuilding a 74 318 Duster and I have a 74 and a 73 wiring schematics.

    I have bypassed the seatbelt interlock by splicing both yellow leads to the interlock relay together.

    I understand how the neutral safety switch works and that the center pole connects to the starter relay and one outer pole is for 12+ From the fuse block via the firewall connectors and the other outer pole is for backup lights that routes thru the firewall connector and on into the rear body harness.

    My question is where do the 3 wires that come from the neutral safety switch connect to the main engine harness. On my car there is a 3 pin connector that is pigtailed off the wiper firewall connector.
    IMG_6354.JPG
    It does not jibe with either schematic but neither schematic shows the seatbelt interlock and the car definitely had the system. There is also a single lead out of this firewall connector that's for the washer pump.
    The car is in the process of being reassembled and not quite ready to plug it all back in and connect battery power just yet. I plan to trace the other side of the firewall connector to see where these 3 leads go once the are in the cabin.
    I am also wondering what the symbol I have circled in blue on this schematic is supposed to represent?
    IMG_5922.JPG
    Any thoughts?
     
  2. RedFish

    RedFish Well-Known Member

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    yep , At one time the reverse lamp wires were inside the cab. The neutral safety wire didn't go into the cab. Just a single brown wire went from neutral safety switch to starter relay. When all this changed they routed the wires through previously unused ports of the bulkhead connector.
    So that 3rd male connector isn't really a "wiper harness" connector. It was called that by some because it had nothing more in it. Neutral safety is brown. reverse lamp wires are purple/violet.If those colors never changed, That's what you find in the dangly add on at bulkhead.
     
    Last edited: Mar 14, 2017
  3. halifaxhops

    halifaxhops It's going to get stupid around here! FABO Gold Member

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    That symbol is a connector,
     
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    • DusterDaddy

      DusterDaddy sledgehammer mechanic FABO Gold Member

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      Thanks, I saw a thread this morning posted by a friend that has a 75 schematic. It shows that configuration with the backup light circuit going into the cabin. In reality on my car, the brown from the nss also goes into the connector. Going to see if it has a mate on the inside maybe to an indicator light? Maybe it passes back out to the engine bay on another pin of the other two connectors?? Now I'm curious as to why they did it.
      For my purposes I think I'll make a nss harness and use the two leads into the cab for the backup circuit and run a new brown lead direct to the starter relay. Thanks for your help!
       
    • halifaxhops

      halifaxhops It's going to get stupid around here! FABO Gold Member

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      I had a engine fire on my 74 se and the wiring diagrams are not right, look at the early Aspen/volarie think I found it there.
       
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      • RedFish

        RedFish Well-Known Member

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        I'm pretty sure the brown was moved there for ease of assembly. Bolt any trans under and plug it in. A clutch safety switch was added to the later models. So the wire would go in there a come back out somewhere else with or without a switch in the path.
         
        Last edited: Mar 14, 2017
      • halifaxhops

        halifaxhops It's going to get stupid around here! FABO Gold Member

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        On mine it come out by the drivers fender by the firewall with a three wire plug then to the "wiper" three prong plug.
         
      • DusterDaddy

        DusterDaddy sledgehammer mechanic FABO Gold Member

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        There is a wire on the inside, brown with yellow tracer. I'll find out where it goes later today.
        IMG_6362.JPG
         
      • DusterDaddy

        DusterDaddy sledgehammer mechanic FABO Gold Member

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        The brown/yellow trace leads to this box under the dash.
        IMG_6364.JPG
        I have my black test lead plugged into it. I was under the impression this box has to do with seatbelt interlock as well
         
      • RedFish

        RedFish Well-Known Member

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        yes sir, Brown did change to brown w/yellow at some point. More tracers are a good thing too since other browns are present. The brown ignition run and brown to windshield washer pump have been connected to wrong places, being in the same general area of engine bay.
        And that white box with so many wires is the warning chime module. I don't know all circuits that went through there in every model.
         
      • halifaxhops

        halifaxhops It's going to get stupid around here! FABO Gold Member

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        Yup that is for the interlock.
         
      • DusterDaddy

        DusterDaddy sledgehammer mechanic FABO Gold Member

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        Well, the brown from the nss goes thru the firewall into the "chime module". I guess would be it comes out on the other connector and makes its way back into the cabin somewhere and heads to the starter relay. Do any of you thinks it would not be a good idea to run a direct brown lead from the nss and bypass the chime box routing?
         
      • DusterDaddy

        DusterDaddy sledgehammer mechanic FABO Gold Member

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        I'm thinking with the seatbelt interlock system, they interrupted the start (yellow) in the chime box as well as neutral safety right here and never had a brown go to the starter relay. They just interrupted the start circuit in the chime box and took care of disabling start there.....
        Possibly there is a starter relay out there that only has terminals for 12+v, yellow start and solenoid??
        Or is that frigging crazy?
         
      • halifaxhops

        halifaxhops It's going to get stupid around here! FABO Gold Member

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        That's what I did much easier than the other way.
         
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        • DusterDaddy

          DusterDaddy sledgehammer mechanic FABO Gold Member

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          Since I don't have the system energized I can only test and trace.
          One more question. Does the brown from the starter relay to the nss serve the purpose of grounding the relay so it will function? In other words, will the nss work and allow the car to start without the two outer terminals on the switch connected? Or does it need the 12v from the backup circuit to function?
           
        • RedFish

          RedFish Well-Known Member

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          Must have a hot and ground, yellow and brown, to the starter relays signal post for it to work. The ground side could be attached directly to chassis ground at the relay but the car would start in gear.
          Reverse lamp circuit is not related electrically, just physically in the same switch screwed into the trans.
           
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          • 89on35s

            89on35s Inferno Red Duster FABO Gold Member

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            Yes, the brown from the NSS grounds the start solenoid. I wired mine straight from the NSS to the start solenoid when I removed all the seatbelt interlock wiring.

            Cley
             
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            • DusterDaddy

              DusterDaddy sledgehammer mechanic FABO Gold Member

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              Anyone know why they routed the drop to the trans out of the wiper connector, behind the motor then down and across the trans? Why no go straight down out of the wiper connector? It would be on the correct side of the trans then.
               
            • RedFish

              RedFish Well-Known Member

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              That connector was for ease of universal assembly. Models, engines, and transmissions varied. Assembly line workers could locate and plug in as req'd, regardless. Wires routed well away from moving parts and/or heat too. 904 and 727 transmissions could arrive at the line with the wires secured in the same place no matter what they were going into.
              Here's another example... Before the dash was installed there was a bit of extra speedometer cable length inside the cab. After dash was installed a worker underneath would pull the excess cable out and toward the drivers seat, then secure it under a sheet metal strap. That cable too could have taken a shorter path.
               
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