Polarity Query

Discussion in 'Tech/Mech General' started by Figaro, Jul 11, 2015.

  1. Figaro

    Figaro Funster

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    I wanted to do a small wiring job in my Hymer (2003) 544.
    There is a locker obviously intended for a 14" crt TV no longer used for housing a TV.
    I wanted to replace the 12 volt socket for a twin USB socket for charging phones / tablets etc.
    There are two wires brown and blue, when I put the multi meter on them : -
    Red probe to brown wire and black probe to blue wire the needle went down :(
    When I put red probe to blue wire and black probe to brown wire it registered 12 v.
    I had expected the brown to be live and blue neutral o_O
    Is this telling me blue is live and brown neutral and is this as it should be ? Or maybe I`m missing something.
    TIA
    Chris
     
  2. scotjimland

    scotjimland Funster Life Member

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    Yes , it can be confusing , Hymer use brown as neutral - and blue as positive. +

    I discovered this when I changed the water pump.. I connected it the 'conventional ' way and it wasn't pumping properly.. then checked and found it was wrong polarity..
     
  3. andy63

    andy63 Funster

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    yes that's what its saying... the blue is positive.. you are using an analogue type meter if it were a digital you would just get a -12v and + 12v to indicate the polarity.
    ta andy
     
  4. hilldweller

    hilldweller Funster Life Member

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    Believe your meter, the Germans use strange colours. I damaged a TV knowing full well the colours were wrong but brain went on autopilot and wired up the TV reversed.
     
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  5. Techno

    Techno Funster Life Member

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    That's why we won the war :LOL:
     
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  6. DBK

    DBK Funster

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    At the risk of muddying the waters, the terms Live and Neutral apply to domestic AC mains supply. For DC supplies the two wires are positive and negative and this is quite different to live and neutral.
     
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  7. Techno

    Techno Funster Life Member

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    Absolutely correct and I usually pick that up but I'm on holiday still :p
     
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  8. pappajohn

    pappajohn Funster Life Member

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    NEVER rely on logic where motorhome wiring is concerned.

    I just fitted a volt meter and dual usb socket in my caravan.

    Voltmeter wiring is blue with white stripe = pos 12v....yellow with white stripe is neg 12v

    Usb wiring is plain blue =pos 12v....brown with white stripe = neg 12v.

    On my RV all major wiring is black.....with grey tracer numbers so small you need the Hubble telescope to see them.
     
  9. tonka

    tonka Funster Life Member

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    Should try an Autotrail.. From memory I think their negative is orange and white !!
     
  10. Techno

    Techno Funster Life Member

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    Pre swift Autocruise too but positive I think?. Not really a problem where the colour is nothing to compare with accepted standards but clearly a BLUE positive and a BROWN negative is designed to confuse the enemy if captured :LOL:
    Top marks to the OP Chris for using a meter!
     
    Last edited: Jul 11, 2015
  11. Figaro

    Figaro Funster

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    Thanks guys, excellent replies as usual (y)
     
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