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Wiring Harness for 12V system with Flathead & 12V Generator

Discussion in 'The Hokey Ass Message Board' started by Doctor Detroit, Aug 17, 2012.

  1. Doctor Detroit
    Joined: Aug 12, 2010
    Posts: 1,004

    Doctor Detroit
    Member

    Hello Gentlemen,
    I need your expertise. I'm ready to buy a wiring kit for my 1951 Mercury. I've got a Flathead with a 12V coil, 12V Generator, etc. What wiring kit will work for this setup?

    From what I've read, American Autowire seems to be a great choice, and I was ready to pull the trigger on a Highway 22 kit. After contacting AAW, now I am more confused. I asked them if the Highway 22 kit would work with a 12V generator, and this was the reply I received:

    "If you are looking for the "stock" generator look in the engine compartment, but with and alternator charging capability (100 amp), I recommend you purchase the PowerMaster generator that is actually an alternator. The stock generator will not supply enought power generation to support the Highway 22 wiring system."

    So how do you guys do it with a Flathead and 12V Generator? I'm wondering if that response was to cover their ass as a liability thing, and the Highway 22 kit will work. Do I need a flux capacitor out of an '85 Delorean?
     
  2. tommy
    Joined: Mar 3, 2001
    Posts: 14,758

    tommy
    Member Emeritus

    I usually get a factory replacement harness made for the vehicle because I often use the factory switches. A universal harness made for streetrods will use new aftermarket switches that look out of place to my eye on the dashboard. I don't want a light switch with a multilingual symbol on it.

    A 12V generator will supply plenty of power for the average flathead powered hotrod. If it's a streetrod with electric fans, mega-watt stereo system and power windos then you might want an alternator to handle the load.

    These universal fit all kits are not built for people that don't want to follow the crowd. A factory replacement harness may cost more than a cheap universal kit but if looks matter to you it might be worth the added expense. It is to me. Once the factory harness is in place then the 12C charging system can be easily adapted. The original 6V switches will handle the 12 power easily they were made to carry twice the amperage in a 6V system.
     
  3. Bruce Lancaster
    Joined: Oct 9, 2001
    Posts: 21,683

    Bruce Lancaster
    Member Emeritus

    If you go with stock harness and the 12V generator is a '56-64 Ford type, it should all just fall together. Wiring diagram for 6 and 12 volt Ford gens is exactly the same. On ignition, only mod would be adding a resistor if the coil you use is specified to use one. The 6V wiring of course is heavier than needed for 12, so you have a lot of safety margin there.
     
  4. Doctor Detroit
    Joined: Aug 12, 2010
    Posts: 1,004

    Doctor Detroit
    Member

    Thanks for the info, guys. I'll probably put a stereo in at a later date, but I doubt it will be a mega-watt deal. It might just be an ipod with a few speakers. No power windows.

    Where do you suggest I find a nice quality factory replacement harness?

    I'm not sure if the 12V generator is a '56-64 Ford type, or just a converted 6V off an 8BA. It looks just like the 6V off an 8BA.
     
    Last edited: Aug 17, 2012
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  5. Bruce Lancaster
    Joined: Oct 9, 2001
    Posts: 21,683

    Bruce Lancaster
    Member Emeritus

    All the normal Ford generators and regulators wire the same way.
     
  6. Doctor Detroit
    Joined: Aug 12, 2010
    Posts: 1,004

    Doctor Detroit
    Member

    I would agree, I don't care for multilingual symbols in my car. This was an Arizona car, and much of it seems to be an decent shape. Do switches generally need to be rebuilt, or do you often have luck with them working after you clean them up a little bit?
     
  7. Bruce Lancaster
    Joined: Oct 9, 2001
    Posts: 21,683

    Bruce Lancaster
    Member Emeritus

    On old Fomoco switches I have rarely found anything wrong...they are very high capacity and won't be working even as hard as stock since the 12 systecuts amperage way down.
    I disassemble them, usually involves simply prying back some tabs carefully. Be REAL careful so you are not surprised by little widgets bounding out and vanishing, lay out the pieces carefully, clean everything and polish the contacts. Slather with white grease, reassemble, repeat every 60 years...mark that on the calendar so you don't forget.
     
  8. TheFrenZ
    Joined: Dec 3, 2004
    Posts: 1,898

    TheFrenZ
    Member
    from Germany

  9. tommy
    Joined: Mar 3, 2001
    Posts: 14,758

    tommy
    Member Emeritus

    That is what I do. I do pry the tabs carefully only enough to separate the pieces. If you should break off one of the metal tabs you can use some PC-7 or other paste type epoxy to hold it together for the rest of your lifetime.:D

    As far as the harness there are probably only a few manufacturers sold by many of the old car parts houses.
     
  10. rotorwrench
    Joined: Apr 21, 2006
    Posts: 633

    rotorwrench
    Member

    There are three sources for harnesses for your 51 Merc. Macs & C&G & maybe others, buy from an outfit up in Oregon or Washington state. I purchased all the stuff from Macs since the prices are all pretty much the same. Rhode Island Wire makes the best ones but they are the most expensive too. Tyree Harris is probably the lower priced source of the three but I have no experience with his stuff. Macs and the others don't tell you that all of the wire harnesses you need are not in one kit. You have to buy all of them seperately. The ones that I can think of right off for example are as follows: The engine compartment harness, The headlight/horn/turn/park lamp crossover harness, the coil wire harness, the overdrive harness if so equiped, the brake light switch harness, the dash harness, the tail light harness, and on and on. There are at least a dozen different little harnesses to make a complete set.

    If I do another car that I'm not concerned with originality on, I'm going to make my own harness utilizing aircraft wire with plain white wire for all circuits. I have a little printer machine that prints on shrink sleeving. I'll use that to ID the wires at each terminal location. The late type aircraft wire is the toughest and most reliable that I've used so far but that's what I'm used to using and can't recommend it to someone who doesn't have the tooling for it. Just finding spools of automotive wire in all the different collors with tracers too is nearly impossible now days. You also have to find it in all the gauges you need as well. Not an easy task.
     
    Last edited: Aug 17, 2012
  11. 51504bat
    Joined: May 22, 2010
    Posts: 1,242

    51504bat
    ALLIANCE MEMBER

  12. Doctor Detroit
    Joined: Aug 12, 2010
    Posts: 1,004

    Doctor Detroit
    Member

    This is why the Hamb is so great... you guys have provided a lot of very useful information that probably would have taken me a long time to accumulate on my own. I've been investigating the factory replacement harnesses, and I realized I would have to double what I was planning in spending - to nearly $1000 - for wiring. Should I dare to buy a factory replacement dash harness, and a universal kit for the body and engine? Or is that just a bad idea?
     
  13. tommy
    Joined: Mar 3, 2001
    Posts: 14,758

    tommy
    Member Emeritus

    I have used partial factory replacement harnesses and finished it with my own wiring. I had to use the factory 32 Ford HL wiring harness to fit the original switch. After that I simply made my own wiring to the H/Ls and tail lights.

    People panic with wiring but if you have some semblance of the original harness remaining it is no more complicated than replacing a fender. One wire at a time until there are no more wires to replace. Old farts like me learned because we had to. There were no hotrod harnesses before Ron Francis. I bought an old 50s? replacement harness for the lights and built the rest myself. It is not rocket science.

    In my opinion it would be much more difficult to marry a modern hotrod harness to an original replacement harness. You would have to understand what the original system did and then how the modern system handles the same thing and try to figure out how to make it work together. Doable but not by a first time wirer.

    To me it would be much easier to use the factory dash harness (expensive) and then just continue the wires to where they originally went on your original harness. Probably less costly too if originality is not an issue. You don't need expensive harness extensions to the rear lights, H/Ls etc. Get a wiring diagram for your car and study it.

    One thing to remember is that you will understand and not be afraid of wiring when it is done. I can still remember the wiring on my first harness and that was over 30 years ago.
     
  14. Doctor Detroit
    Joined: Aug 12, 2010
    Posts: 1,004

    Doctor Detroit
    Member

    Update:
    I purchased factory reproduction wiring harnesses from Macs Auto Parts. These part numbers are for a 1951 Mercury. 1949 or 1950 may use different part numbers. I also purchased a Painless Wiring 18 circuit Fuse Box #30003.

    1M-14401-A is a Dash Wiring Harness
    1M-14405-B is a Body Wiring Harness
    1M-14486-A are Turn Signal Wires inside steering column
    1M-14445 are Headlight Crossover Wires
    1M-13076-A are Headlight Socket Wires - 2 required
    V12871 is a Voltage Reducer for gauges

    http://macsautoparts.com/1949-59-ford-mercury-electrical-wiring/camid/F50/cc/1055/

    http://www.painlesswiring.com/Manuals/30003.pdf
     
  15. 49dreamer
    Joined: Apr 19, 2011
    Posts: 75

    49dreamer
    Member

    I hope you do a good job of posting your progress on wiring your car because I might be right behind you doing the same thing to mine. I've already purchased the same steering column wiring kit for mine.
     
  16. Doctor Detroit
    Joined: Aug 12, 2010
    Posts: 1,004

    Doctor Detroit
    Member

  17. Blake84
    Joined: Feb 4, 2012
    Posts: 729

    Blake84
    Member

    I just used a speedway 12 circuit kit on my flathead v8 super easy and super affordable like $160
     
  18. judder_man
    Joined: Dec 5, 2011
    Posts: 163

    judder_man
    Member
    from U.K.

    Can someone answer another question on topic? I want to convert my 50 to 12v but do i need to use a resistor in line to the gauges? Thanks for the info.
     
  19. Doctor Detroit
    Joined: Aug 12, 2010
    Posts: 1,004

    Doctor Detroit
    Member

    You need this from Mac's or elsewhere:
    V12871 is a Voltage Reducer for gauges
     
  20. judder_man
    Joined: Dec 5, 2011
    Posts: 163

    judder_man
    Member
    from U.K.


    Thanks, it it one reducer/resistor in line for the supply to the gauges? Is there any other alterations needed to protect any other circuits?
     
  21. You're going to need a ballast resister to the points in your distributor, if you are going from 6V to 12V. If you have electric wipers, or a 6V heater blower motor, you will need voltage reducers for those.
    You may have to do something with your fuel sender, although in theory they aren't supposed to be voltage sensitive.
    For what it's worth, I just finished a rewire on a 47 Ford with a harness that was in the trunk when I bought the car. Don't even know what brand it was. The harness was for some sort of late 60's/early 70's GM car. It didn't take a lot of effort to make the thing fit the old Ford, and I was left with more circuits than I'll ever use. I used the original switches, They work fine.
    It's not too difficult fellas. All it takes is some thought as you go along to make sure you get the wire in a protected place.
    There is a lot of comfort in going out, jumping in the rod, and knowing that your lights, and charging system will get you home.
    The effort you put in now will pay you back in spades for a long time.
     
  22. I used the speedway wiring kit on my 36 ford.worked great.with a flathead 12v.$130.
     
  23. Doctor Detroit
    Joined: Aug 12, 2010
    Posts: 1,004

    Doctor Detroit
    Member

    Attached Files:

  24. I used the same Speedway harness with the '57 Ford generator on my flathead and I am very satisfied with the results. But I have no radio/stereo or electric fan I am running an electric fuel pump though.
     

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