Good Method to Add Wiring For Add-Ons

Electrical and Ignition

  1. SpeedThrills

    SpeedThrills FABO Gold Member FABO Gold Member

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    Yep, that’s the one. Thanks
     
  2. SpeedThrills

    SpeedThrills FABO Gold Member FABO Gold Member

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    Thanks. I just downloaded it. Last I heard, thy didn’t have the 74.
     
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    • 4spdragtop

      4spdragtop CONGRATS NORTH AMERICA! FABO Gold Member

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      Maybe find someone on here with OEM schematics? And get a copy. I was using 67 schematics from mymopar assuming they were oem, they werent, they were scanned from a Motors Manual.
       
    • SpeedThrills

      SpeedThrills FABO Gold Member FABO Gold Member

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      This pic is a section of what I printed out from mymopar.com.
      What I need to know, and what it doesn’t show, is where the brake failure light circuit gets its 12v. The fuse it goes to is good, and everything else on that fuse works.
      I am powering an accessory fuse block that I added through it. (Powering the relay) It stopped working when I welded on the car and forgot to disconnect the battery. :(
       
    • SpeedThrills

      SpeedThrills FABO Gold Member FABO Gold Member

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      A upload_2022-5-14_16-19-14.jpeg
       
    • mopardude62

      mopardude62 FABO Gold Member FABO Gold Member

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      That circuit is a little different as it should be getting 12v through the fuse (which you have verified is good) and it’s grounded when the brake light switch moves off center inside the proportioning valve.
      My guess would be the 12v comes from the circuit board behind the instrument panel, through the brake light on the dash, through the fuse and out cavity M to the switch to be grounded.
      Could you have been pulling 12v from the instrument panel, through the bulb and the bulb is burned out? That would cause an open in the brake circuit when everything else is working.
       
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      • mopardude62

        mopardude62 FABO Gold Member FABO Gold Member

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        If you see the voltage limiter in the upper right, follow it out to the left and down through the bulb, through junction CE2 (the bulkhead) and down to the brake switch.

        B4ABAB04-2C89-44E6-879C-DF4B9D68D4E5.jpeg
         
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        • 4spdragtop

          4spdragtop CONGRATS NORTH AMERICA! FABO Gold Member

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          Are you sure that's OEM? Those look very similar to Motor Manual. Just wanna be sure...
           
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          • mopardude62

            mopardude62 FABO Gold Member FABO Gold Member

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            Steve, the pics I sent are from my 1974 service manual.
             
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            • 4spdragtop

              4spdragtop CONGRATS NORTH AMERICA! FABO Gold Member

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              Do you have a pic of exact same part of schematic that @SpeedThrills posted? Just trying to verify that his pic is big factory schematics.
               
            • mopardude62

              mopardude62 FABO Gold Member FABO Gold Member

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              Steve, no I don’t have those drawings they are not in the 1974 service manual
               
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              • SpeedThrills

                SpeedThrills FABO Gold Member FABO Gold Member

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                All I know is that diagram is from mymopar.com.
                 
              • 4spdragtop

                4spdragtop CONGRATS NORTH AMERICA! FABO Gold Member

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                That is where I THOUGHT was OEM(for our 67), but wasnt. Chasing my tail for a while until I realized it was from Motors Manual. I since found the factory 67 supplement for our 67 cuda from @Mattax Seeing how it was 1st year for 2nd gen cuda, Ma Mopar "forgot" to put barracuda specific schematics in the FSM. Sorry not trying to confuse/ derail, just want you to be aware of possible differences in schematics.
                 
              • Mattax

                Mattax Just the facts, ma'am FABO Gold Member

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                From somewhere I have a partial digitized '74 electical section. Might have been from FABO a few years back.

                @mopardude62 analysis looks correct to me.

                Pull the hand brake with the key on, the brake light lamp should light up.
                upload_2022-5-14_18-43-0.png

                Wire codes:
                J2 is Ignition. So key in run, it is hot
                G was probably Gages
                P maybe was Parking Brake originally
                 
                Last edited: May 14, 2022
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                • SpeedThrills

                  SpeedThrills FABO Gold Member FABO Gold Member

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                  I guess that’s a good possibility. I have some dash lights that aren’t working. When I get to that, I’ll look into this more. in the meantime, I’m powering the relay from the blue field wire. I measured 11.2 volts, and it’s working fine.
                  Great information. I’m learning a lot about the wiring in this car. Thanks all.
                   
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