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Hot Rods 6 volt, positive ground to 12 volt, negative ground

Discussion in 'The Hokey Ass Message Board' started by rockin rebel, Nov 11, 2014.

  1. I am going to do it, just wondered, beside the obvious, starter, gen., bulbs, ect. what is the deal to change the grounds.?? if any... thanks......on a 47 Plymouth..
  2. jseery
    Joined: Sep 4, 2013
    Posts: 743

    from Wichita KS

    6v wiring is a heaver grade than 12v so that is not an issue. There is no changes required to the basic wiring, the only issues are any retained 6v items you want to power, such as instrument gauges. You need a voltage reducer for each item that reduces 12v to 6v. And as stated, change the bulbs and whatever to 12v. Make sure the ignition coil is wired for the correct polarity and a ballast resister in installed.
    SanDiegoHighwayman likes this.
  3. Slopok
    Joined: Jan 30, 2012
    Posts: 2,625


    You should be able to retain the 6 volt starter, it'll crank faster than it idles. You will also need a 12 volt coil.
  4. Out of curiosity, is there a reason to switch it? I've thought about changing over and couldn't come up with a real "need" to change. I have 4 six volt cars including one that's positive ground.

  5. If your wiring is in good condition and working well, there's no mechanical reason to change. The biggest downside is the availability of replacement parts these days as it's been almost 60 years since the last Detroit 6v cars rolled off the assembly line. Even 6v lamps aren't so easy to find anymore...

    But a 6v system is much more sensitive to voltage drops from degraded connections. Voltage drop has nothing to do with the system voltage, but is entirely due to the amps in the circuit and the resistance (which can be a poor connection and/or wire size). So for an example, a 50W headlight will draw 8.3 amps at 6v. If you have a .5V drop, that's a 8% drop and will be noticeable as a dim light. Convert to 12v, use the same wattage lamp (which at 12v uses half the amps), and the drop goes to .25V and the percentage drop is now only 2%.
    loudbang and SanDiegoHighwayman like this.
  6. Thanks Steve- I guess since I don't daily my 6 v cars I haven't worried much about replacements. My daily is a not to be spoken of here '68 with that new fangled 12 volts electrical system.
    Lloyd- Please excuse my hijacking.
    SanDiegoHighwayman likes this.
  7. hey, no problem, we all need to know the, ;whys' of theses things...i just want the ease of 12 volts, stereo ect, faster start,, headlight bulbs....
  8. SanDiegoHighwayman
    Joined: Jun 26, 2012
    Posts: 951


    Dont fergit to WATCH OUT FER them POWER WINDAHS! *they* kin become gullitiones fer littl kids foolin w em when they're 6 bein driven by 12! My 55 Merc Monterey "woody" shure started up right QUICK when I converted it to 12 :O


    But then, SO did *I* when my "racked" [ she had a NICE rack as well ] woman pushed *MY* button ;) :)

    In PRAISE of "older" women!

    Ah, THEM were THE days! :) [ summer -- thru -- fall of 83 -- ]

    Aside from switchin the polairty & installin a 1 wire alternator & goin w 12v bulbs & headlamps, new coil w ballast resister and 12v starter solonoide w coil shunt -- I don't remember havin to DO anythin else -- gas guage worked on 12, and i'd put in mechanical SW guages into the spedo housin w a voltmeter instead of an ammeter --- everythin was workin well last I saw of thet car and her --

    LIKETA have the *CAR* back ;) :)

    my littl kids survived it :)
    Last edited: Nov 11, 2014
    loudbang likes this.
  9. Rusty O'Toole
    Joined: Sep 17, 2006
    Posts: 9,489

    Rusty O'Toole

    Do yourself a favor and keep it 6V. You will save a lot of money, time and aggravation if you just fix what is wrong with it and leave the 6V in it.
  10. Atwater Mike
    Joined: May 31, 2002
    Posts: 10,514

    Atwater Mike

    ...Not to mention the removal and reversing of direction of all the wires to change to Negative Ground!
    Don't stop for a break...this is a complete reversal of voltage direction...
    Hnstray likes this.
  11. 55Brodie
    Joined: Dec 15, 2008
    Posts: 746


    The only wires needing to be changed are battery cables, coil and ammeter if equipped.
    SanDiegoHighwayman likes this.
  12. lincolnlog
    Joined: Feb 25, 2007
    Posts: 186

    from Arizona

    Coil, bulbs and radio. All else can stay..... That is if your 50+ year old wiring is good. unlikely!
  13. lincolnlog
    Joined: Feb 25, 2007
    Posts: 186

    from Arizona

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