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Technical voltage reducer for dash gauges wiring??

Discussion in 'The Hokey Ass Message Board' started by bigbadad, Dec 9, 2015.

  1. bigbadad
    Joined: May 7, 2007
    Posts: 47

    bigbadad
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  2. The37Kid
    Joined: Apr 30, 2004
    Posts: 27,267

    The37Kid
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    I'd like one of the people blessed with the God given gift of understanding electricity to explain how it works to the simple minded. Bob
     
  3. Jalopy Joker
    Joined: Sep 3, 2006
    Posts: 25,187

    Jalopy Joker
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    ad says "clearly illustrated diagram included"
     
  4. KoolKat-57
    Joined: Feb 22, 2010
    Posts: 2,968

    KoolKat-57
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    from Dublin, OH

    Try This...... For assistance, call (877) 230-9680 Mac's hotline.
    KK
     

  5. Ebbsspeed
    Joined: Nov 11, 2005
    Posts: 5,115

    Ebbsspeed
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    Post an image of that "clearly illustrated diagram" so we know which of the three wires goes to ground, battery, and the gauges. Probably goes something like this, which shows the gauge wiring from a 38 Ford. Reducer.jpg
     
    Last edited: Dec 9, 2015
  6. vtx1800
    Joined: Oct 4, 2009
    Posts: 1,068

    vtx1800
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    I don't have the pictures but I used their product to use the six volt gauges (in the avatar at the left) and they just got on the "hot" side of the gauge and 12 volts goes to the screw on the "board" with the electronic gizmo. You use one voltage drop per electric instrument.
     
  7. Ebbsspeed
    Joined: Nov 11, 2005
    Posts: 5,115

    Ebbsspeed
    ALLIANCE MEMBER

    You're probably talking about a Runtz reducer, like in the pic below. His is a three-wire reducer, they are wired differently, and can power multiple gauges.

    Runtz.jpg
     
  8. Save yourself a bunch of money and wire up some LM7806 electronic voltage reducers. These 7806 reducers have a 1 amp capacity, good for 1 gauge. Search on HAMB here to see pics and wiring of the 7806, but you can buy 10 of them on ebay or similar for a few $. Input is 12VDC, output is 6VDC. I have one on my 37 Chevy gas gauge and it works great.
     
  9. 55Brodie
    Joined: Dec 15, 2008
    Posts: 746

    55Brodie
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    That MAC unit is a solid state device and should be more reliable than the Chinese copy of the Ford Instrument Voltage Regulator that uses a bi-metallic strip to pulse the DC voltage to an average of 6 volts. One wire is ground, one is for the switched 12 volt source and one wire to power the gauge(s).
    I prefer the Runtz reducers, one per gauge. I have had 13 trouble-free years with them in my 55.
     
  10. Blues4U
    Joined: Oct 1, 2015
    Posts: 4,821

    Blues4U
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    from So Cal

    It probably just uses a circuit with a MOSFET (type of transistor) wired as a switch, that turns off when voltage hits a certain point (6v). The switching occurs at a very high rate of speed, as the voltage approaches the cut off point the circuit is opened and the current stops flowing, which will cause a drop in voltage, which will turn the switch back on and allow current to flow again until the voltage reaches the cutoff point again. It may include some capacitance to smooth the current flow. As 55BRodie said, it is a solid state device with no moving parts. At most it it may be subject to damage from heat, but seeing as how they've encapsulated it in a sealed unit they've probably accounted for sufficient dissipation, as long as you don't over load it with current.

    MOSFET's are very useful little buggers and can be used for all sorts of things.
     
  11. Ebbsspeed
    Joined: Nov 11, 2005
    Posts: 5,115

    Ebbsspeed
    ALLIANCE MEMBER

    More likely it uses a 6-volt zener diode for reference voltage and a PNP transistor with the appropriate heat sink required to support it's advertised current rating. It could well be an encapsulated 7806 regulator, which is basically what I described, but with current limiting and thermal shutdown built in. A 7806 will support current of more than 1 amp with appropriate heat sinking.
     
  12. Pewsplace
    Joined: Feb 10, 2007
    Posts: 2,770

    Pewsplace
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    I have only used the Runtz and they work perfect. One per gauge, easy to install and about $15 each.
     
  13. bigbadad
    Joined: May 7, 2007
    Posts: 47

    bigbadad
    Member

    Which obviously I haven't got, hence my post

    Not so easy from UK when I'm working in the morning and all of Mac's is asleep...


    Thanks for everybody else's replies, I've managed to find out:

    GREEN goes to ground.
    RED goes to the ignition switch
    BLUE goes to the gauges

    Cheers
     
  14. I am going to fathom a guess and say that this is correct. One hot one ground and then daisy chain the gauges.

    If it were my lucky day and I was wiring it I would probably throw hot at the red and earth at the green and run my gauges off of the blue, but it would have to be my lucky day or that would absolutely be wrong.
     
  15. KoolKat-57
    Joined: Feb 22, 2010
    Posts: 2,968

    KoolKat-57
    Member
    from Dublin, OH

    Not so easy from UK when I'm working in the morning and all of Mac's is asleep
    Didn't see your location, I will be more careful in the future.
    KK
     
  16. The37Kid
    Joined: Apr 30, 2004
    Posts: 27,267

    The37Kid
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    OK, if it turned out to be your bad day or an attempt by me what is the worst case scenario, fried instruments and a fire that takes out most of the interior? Bob
     
  17. Blues4U
    Joined: Oct 1, 2015
    Posts: 4,821

    Blues4U
    Member
    from So Cal

    Jeeeez, just put a volt meter on it and check the output before you connect it to your gauges. A multi meter is a too should be in everyone's tool box. Get a cheap one and learn how to use it.

    https://www.google.com/webhp?source...e=UTF-8#q=ebay+multimeter+test+meter&tbm=shop
     
  18. The37Kid
    Joined: Apr 30, 2004
    Posts: 27,267

    The37Kid
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    Thanks for the link Blues, as with all things electrical there are right and wrong things, which multimeter is the right one to have, and are they also a voltmeter?
     
  19. Worse case scenario is that I hook it up with one lead loose and check voltage coming out of it. The shunt is going to get warm when it is working, but not hot like a normal ceramic resistor, and it should have 6v coming out of the blue pigtail. if it does you're golden.
     
  20. Blues4U
    Joined: Oct 1, 2015
    Posts: 4,821

    Blues4U
    Member
    from So Cal

    All of those meters include a voltmeter, selectable ac/dc, they will also have an ohm meter w/ diode check function and an amp meter (low current measurements only). For a DIY'er these are invaluable tools, must have's. Which one to get is subjective, like most tools you get what you pay for. But even the cheapest ones will do in a pinch. I have several meters, mostly digital, but I like analog meters (with an actual needle) for throwing in a tool box in the trunk. For the shop, buy one that is nice enough you can trust the readout, but won't break the bank. Fluke is the recognized leader in digital test meters, but they are expensive and really IMO only needed for the professional. That 20 dollar Craftsman meter would be fine for everything a DIY'er would need to do.

    And check out some of these links for learning how to use it:
    https://www.ifixit.com/Guide/How+To+Use+A+Multimeter/25632
    http://nadp.sws.uiuc.edu/cal/PDF/MulltimeterUse.pdf
     
  21. d2_willys
    Joined: Sep 8, 2007
    Posts: 4,103

    d2_willys
    Member
    from Kansas

    Go get a multi-meter at Harbie! $2.99 is cheap insurance for old gauges that are expensive to replace.
     
  22. LOL I used a 7 dollar radio shack digital for between 15 and 20 years. it just gave up the ghost in August. I have I think 3 very expensive analogs and I use those for anything that is really technical but my digital was my go to for basic trouble shooting.
     
  23. hotrod428
    Joined: Feb 7, 2007
    Posts: 287

    hotrod428
    Member

    Why not just use a Mopar coil resister, I put one on my tractor 20 years ago to power the gauges when I converted it to 12 volt and its still working fine.
     
  24. Blues4U
    Joined: Oct 1, 2015
    Posts: 4,821

    Blues4U
    Member
    from So Cal

    You're talking about a ballast resistor, right? A ballast resistor works by following the principals of Ohm's Law, i.e. voltage = current x resistance. The size (resistance value and wattage) of the ballast resistor is determined by the current draw of the ignition coil. If the gauge cluster happens to draw about the same current as an ignition coil, than that would be fine. If it doesn't, than the voltage may end up being too high or too low. A voltage limiter doesn't require a specific current draw to limit the voltage, that's why you would use it instead of a large resistor.
     
  25. Boys and Girls it doesn't get much simpler than this "Dash Gauge Resistor".

    [​IMG]
    $ 3.25 US available on eBay. Clips voltage to 6.8 volts. A lot closer to the voltage that a good well charging 6 volt system would be. We have sold tens of thousands to date without a single problem. Satisfaction guaranteed.
     
    Last edited: Apr 15, 2020
  26. The37Kid
    Joined: Apr 30, 2004
    Posts: 27,267

    The37Kid
    Member

    ^^^^^^^^^^^^^^^^^ Can you take the time to explain what the gizmo is and what it does, not everyone understands electricity. Bob
     

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