What do I need for a proper under-dash rewire?

Discussion in 'Electrical and Ignition' started by Chained_360, Nov 26, 2018.

  1. Chained_360

    Chained_360 FABO Gold Member FABO Gold Member

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    I need some help determining what I need/what route to take with patching up the under dash wiring on my '68 notchback Barracuda. I drove it while I was home for Thanksgiving, and while investigating why my turn signals, aftermarket tach, and blower motor were intermittently shutting off, I discovered that the wiring under my dash is a good bit messier than I thought. Dangling connectors, wire screws, wires just straight up tied together next to insulation... It's a bit of a miracle this car hasn't caught fire.

    I've already been planning to pull the cluster to repair some things behind it, but now I'm realizing that I should definitely do a complete rewire or at least patch things together. I can't afford a $600 brand new under dash harness, so what would you all suggest I get in order to do a good, solid repair/rewire job? I know how to solder properly and whatnot, I actually love wiring and electricity, but I just lack exoeriexpe. Should I get a bunch of colored wire or reuse/repair the factory stuff? What tools for crimping and splicing do you suggest? Anything I should know about dash wiring that would be good to be aware of on a '68 notch?

    If it helps any, the car is a 1968 Barracuda notchback, factory 318 car (now has 360/904), no A/C, 3-speed wipers, manual steering and brakes, suspected to have had a map light switch during it's life (now missing), nothing special in terms of rear defogger or fancy options.
     
  2. halifaxhops

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

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    If you are good at wiring do what I did with my engine compartment. You can buy all the color wire you need on line in lengths, get a good Packard 56 terminal kit and good crimpers, a removal tool and go for it, not that hard. Just take it out lay the old one out and do one wire at a time. Reuse the connectors that you can with new terminals and also have a wiring diagram around easy to order the wire that way in the proper size and color. Think mine cost about 120 total to do with all the tools and parts. USE GOOD WIRE!
     
    Last edited: Nov 26, 2018
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    • halifaxhops

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

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      • rklein383

        rklein383 Well-Known Member

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        Its the old adage; how do you eat an elephant, one bite at a time. Same thing goes for the wiring harness, one fix/wire at at a time.

        When I went through mine, i removed all the harness tape and used little zip ties to maintain the original configuration. I inspected every wire and connector. If the wire was still flexible, not heat damaged, I kept and/or repaired. All splices were done with solder and heat shrink tape.

        One thing I also did was I found a wiring diagram. Enlarged it and put it on a piece of cardboard so I could easily reference the diagram while working on the harness.

        You can do it, It really is not that hard. One wire at a time.

        Rod

        IMG_3879.JPG
         
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        • Syleng1

          Syleng1 Karma is real and Life is short... FABO Gold Member

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        • RedFish

          RedFish Well-Known Member

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          If it had a map light it likely had the lighting group which included a delay timer on the dome lamp circuit. You might find a tiny light bulb above the ignition switch bezel too. When that delay timer would fail, the owner might hack a lot of stuff trying to end the dome lamp always on and battery kill. Sure I'm only guessing why the wiring was hacked but there had to be some reason for it.
          So.. repair the conductors per the diagrams. Once every component is properly connected and chassis grounded then you find which components need replaced.
          I'll add that if it were mine, I would totally delete that lighting group. I do use the basics, a glove box lamp or the trunk lamp, but I don't need the dome lamp to remain on while I dig my keys from my purse. Nor do I plan to spread a Rand-McNally road map on the passengers seat and floor.
          I can't honestly speak to the lighted key switch issue. Mine is in a chromed bezel. Maybe the 68 model key hole is more difficult to see/ring under that odd shaped color keyed bezel. My total delete plan would delete that lamp too. Anyway, Good luck with it.
           
        • Mike69cuda

          Mike69cuda 63 is the new 17 FABO Gold Member

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          I don’t know if it puts you closer in range on cost, but both Classic and year one have sales that can get you 30% off or so. That’s what I did.
           
        • 89on35s

          89on35s Inferno Red Duster FABO Gold Member

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          Get ahold of a factory service manual, pull the harness out and go through it wire by wire until it is back to factory. Think about your aftermarket accessories (tach, stereo etc) while you are doing it and make provisions for them. An added bonus of doing this is you can troubleshoot easily after because you know exactly what goes where. Grabbing an assortment of Packard 56 connectors is a must. I got mine on Ebay. Also if you have a spare wiring harness from a parts car, they are invaluable for little bits you cant easily source elsewhere.

          Cley
           
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          • 4spdragtop

            4spdragtop FABO Gold Member FABO Gold Member

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            I'm thinking of a rewire under dash on 67 cuda not looking fwd to it. No way around pulling the dash really. Console and ac just to add to the challenge. Windshield has to come out for dash removal. Snowballs quickly into a shit show lol.
            I'll be following along here
             
          • j par

            j par Well-hung Member

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            Actually after you've done it it becomes unbearably simple.
             
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            • Chained_360

              Chained_360 FABO Gold Member FABO Gold Member

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              Thank you! I don't have the lighted ignition bezel, so I'm not sure what the deal is. The fender tag didn't say anything about it being an option on my car, the only lights it has right now are the dome light and glovebox light. There's a hole in the dash down low about where a map light switch should be

              I looked at that, and at least on classic's site, wiring harnesses are marked as non-discount items. Even then, too much $$$ :(

              That's what everyone seems to be saying, is the Packard 56 connectors are the way to go.
              Sounds fun:poke:. I won't be doing this until around Christmas time, and it will most likely be a different thread. There will be lots of pictures!
               
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              • j par

                j par Well-hung Member

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                Just remember when you buy a wiring harness it doesn't jump out of the package under your dash. You're going to have to take it all out and disconnect every last one and reconnect a foreign one in there. Much easier and much cheaper to repair what you have, your taken it out anyways....
                 
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                • Mike69cuda

                  Mike69cuda 63 is the new 17 FABO Gold Member

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                  Year One has the harness for $519, discount eligible, with a 30% discount. That is about $363. I have found that the price varies wildly on some of the more expensive stuff, so you need to check a bunch of sources. Probably still a lot more than you can do it yourself for, but it does come with a new fuse box which is nice, as water leaking from the windshield wiper grommets usually kills the fuse box.

                  Make sure you replace connectors on the mating harnesses too and use dielectric grease. The engine bay harness may also be a good one to replace also.
                   
                • Chained_360

                  Chained_360 FABO Gold Member FABO Gold Member

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                • Mattax

                  Mattax Just the facts, ma'am FABO Gold Member

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                  The only extra item there is the tach, and that's pretty easy to wire in.
                  One thing those three items have in common is their power goes through the ignition switch and the fuse the box.

                  If you solder and use heat shrink, as long as there's enough slack, that will work for splicing.
                  There is one big splice that was originally welded. That's the main power distribution. Rarely a problem there, but if there is, obviously you'll have to fix it.
                  All of the terminals inside connectors were crimped. Use crimpers for open barrel terminals. Some will crimp both the main and the strain relief folds in one shot.
                  Very few if any will technically have the Packard 56 (sometimes sold as Delphi 56). Most if not all in your '68 will look more like a Packard 58, also called Chrysler or Ford style. I'm sure someone knows the history but I don't. In general they are interchangable, fitting the same connectors. More important to use the correct ones for the wire sizes.
                  Need help on bulkhead wiring
                  Sources for Chrysler type wire terminals
                  Reuse the factory stuff if its in good condition and it won't be strained by the reduced length. If just some the insulation is all brittle and cracked, its possible to slip some heat shink over the section after removing the terminal. I did that on a few of my wagoneer's wires using colored and clear shrink. Otherwise, replace the wire or section of it. If the copper itself is showing corrosion or oxidation under the insulation, that's no good.

                  Wire. I buy locally from a marine supply. Lots of colors. Good quality, and can purchase by the foot. Lots of other options. A few listed in the linked threads.

                  Especially since its been cut into, print off a few copies of the '68 Barracuda wiring diagram. This way you'll see what's been done and needs be fixed.
                  You'll have to make your own cable and routing diagrams.

                  Other things: A terminal release tool is handy and helpful
                  You'll want to remove the bulkhead connectors, and then you can remove the female terminals from the inside. Make sure they are clean and not showing damage.
                  question on the main harness plug on firewall
                  Connections to the instrument panel circuit board are a little different.
                  Cable bundling. A non-adhesive electrical tape was used. I think vinyl, not cloth, is what you'll find. Some of the body wiring may have cloth loom on it. My '67 has that on the wire bundle going to the fuel sender and tail lights etc.
                   
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                  • halifaxhops

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

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                    Ebay has them and Rhode Island wiring also.
                     
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                    • Mattax

                      Mattax Just the facts, ma'am FABO Gold Member

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                      Power for fused circuits that are on only when the key switch is in run or acc comes from the wire marked Accessory. It goes to the fuse box even though I didn't label it.
                      upload_2018-11-26_11-10-32.png
                      The big black dot represents the main junction.

                      More crimping illustrations here:
                      International Full Size Jeep Association - View Single Post - Cold Temp/humidity sensitive Ignition
                      The crimpers from American Wire are nice, but a bit pricey.
                      The ones Halifaxhops posted look good.
                      I'm using a set from Astro Tool with interchangable jaws. Downside is the open barrel jaws are little too wide for some of the male terminals. Otherswise I like them.
                      Some more rewiring guidance in this one
                      WIRING NIGHTMARE

                      Twin lock and pin type connectors shown in the back pages of this pamphlet
                      Electrical Wiring (Session 247) from Chrysler Master Tech
                       
                      Last edited: Nov 26, 2018
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                      • PocketAces

                        PocketAces Well-Known Member

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                        You also get a new bulkhead connector which is a common source of problems on these cars due to the high current passing through to the amp gauge.

                        I think the engine harness is quite a bit cheaper, and usually in worse shape due to engine heat.
                         
                      • MomsDuster

                        MomsDuster FABO Gold Member FABO Gold Member

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                        The two most important things IMO are:
                        1) Time, take your time.

                        2) Patience, lots and lots of patience
                         
                      • RedFish

                        RedFish Well-Known Member

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                        The wiring harness will come out without pulling the entire dash.
                        If you'll separate the bulkhead connectors outside and shove that box into the cabin, drop the light switch and the wiper switch at bezel nuts, same with flasher modules, bring those out still connected, 1 screw in the fuse box, connectors behind the left kick panel, Pull the instrument panel, get the harnesses branches out from under the very few straps...
                        Yeah there's a brake lamp switch connector, reverse lamp connector, blower switch connector, and another at blower resistor pack, glove box lamp, wire to right door jamb switch.
                        If you think that reads like a LOT, remember its nothing compared to later models.
                         
                        Last edited: Nov 26, 2018
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                        • Kent mosby

                          Kent mosby FABO Gold Member FABO Gold Member

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                          Would it be easier to remove the dash for access to replace the entire harness? Can you do that without removing the windshield? My seats are out so there is room to move around but I will be replacing mine soon on a 73 scamp.
                           
                        • RedFish

                          RedFish Well-Known Member

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                          The bolts that hold the dash to the firewall are installed from top down underneath the windshield gasket. You would pull inst' panel,heater case, etc.. to go under there with a di grinder and cut 5 bolt locations.
                           
                        • j par

                          j par Well-hung Member

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                          I seriously thought about coming from behind and putting them in backwards?
                           
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                          • RedFish

                            RedFish Well-Known Member

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                            I did pull the windshield for another reason but also put a cut dash for my custom instrument panel in it ( all of the original dash hanging on the wall ). So I did install those 5 bolts from bottom up. The U nuts weren't much taller than the bolt head and the bolts weren't too long. Simply flipping the OEM hardware on my 67 might not apply to all models. If nothing interferes with the gasket lay....
                             
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                            • 4spdragtop

                              4spdragtop FABO Gold Member FABO Gold Member

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                              I hear what you are saying Ben, thanks. I was thinking of painting dash, that's why a possibly complete removal.
                              Thanks for the tips!