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eletrical question

Discussion in 'The Lounge' started by surpip, Apr 13, 2007.

  1. surpip

    surpip 1 ton status

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    Our shop truck is a 34 ford with a flad head, the eletricla system was converted to 12v but there is still a lot of 6v stuff on there, like the wiper motor.
    I used an old reostat to try to knock the voltage down, but it is still to much for the motor.
    My question is, what size resitor do i need to wire in line to make the voltage drop from 12 to 6-8v?
     
  2. skyyk5

    skyyk5 1/2 ton status

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    They have stuff out there for that. JC Winteny has a voltage drop just for that. And might find more info in the garage.
     
  3. surpip

    surpip 1 ton status

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    ya i ment to post this in the garage
    Paging mods:)
     
  4. mofugly13

    mofugly13 1 ton bucket of rust Premium Member

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    Take a look at this page

    http://www.the12volt.com/ohm/ohmslaw.asp

    You need to get a current reading off the wiper by running it from a 6V source and measuring the current draw. Then plug that into R=6/I and that will give you your resistor value. That's how it works in general DC circuitry, but I am not sure how it applies to automotive wiper motors. You can find the appropriate formula on that same page to figure out the needed power rating (watts) for the resistor as well.
     
  5. surpip

    surpip 1 ton status

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    thats the big problem, is finding a 6 volt source

    I might just use a old ballast resistor
     
  6. kgillyk5

    kgillyk5 1/2 ton status

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    That's really it...The last part is really important. Just knowing the resistance is great but the resistor needs to be able to disipate the heat (volts X amps=watts) that the current is producing.

    Oh ya, I=Amps...nobody tells you that.
     
  7. 84k5

    84k5 1/2 ton status

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    Call the engineering department of the manufacture of the wiper motor and get a recommendation. Then you have a scapegoat when the car catches on fire.:wink1:
     
  8. surpip

    surpip 1 ton status

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    you bet
    that will work great, since the truck in a 1934
    I'm sure the guy that designed it is still alive
     
  9. kgillyk5

    kgillyk5 1/2 ton status

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    If the things worth anything, I say get a 12 volt wiper system or whatever other accessories you need. Will make working on it later easier. I've got a linkage and 12v wiper motor from a 94' furd probe you can have.
     
  10. surpip

    surpip 1 ton status

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    no its need to be the stock motor
    here is the truck

    114-1411_IMG.JPG

    113-1373_IMG.JPG
     
  11. kgillyk5

    kgillyk5 1/2 ton status

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    Man, I love that thing...saw it in some other post before. I was thinking like a big ol' service truck or something.:haha::haha:

    Ya, go original. So the start and charge is all 12 volt??? Need dc to dc converter at the right wattage to run acc....Cool.:D
     
  12. 84k5

    84k5 1/2 ton status

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  13. surpip

    surpip 1 ton status

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    it worked
    I called you out to search for me
    heheheh


    thanks dood



    although i am pretty sure no one at a ford dealership would be able to look up the specs on that old of a part
     
  14. kgillyk5

    kgillyk5 1/2 ton status

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  15. surpip

    surpip 1 ton status

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    awsome, thanks guys for the help
     
  16. RustyParts

    RustyParts 1/2 ton status

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  17. surpip

    surpip 1 ton status

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    no an option, my boss is cheap
     
  18. CustomChevy

    CustomChevy 1/2 ton status

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    steal a squeegy from the local gas station


    problem solved.
     
  19. RustyParts

    RustyParts 1/2 ton status

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    Well, if your boss is too cheap, using Ohms law if the windshield motor is pulling say 15 amps, on a 12 volt system you would need a .8 ohm resistor to drop six volts.
     

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