Wire passing continuity but no voltage...

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  1. #1
    Not Wurm Isezumi's Avatar
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    Wire passing continuity but no voltage...

    I was trying to crimp some custom 4 pin molex extensions and wires and they are being extraordinarily fussy. Each warness will pass continuity to each other, even in the chains. But if I attach one to the a running PSU I get no Voltage reading.

    I had to solder a few lines together to conserve harness...could a poor connection via solder allow continuity but hinder voltage draw?

  2. #2
    White Shark Moderator Moridin's Avatar
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    You could have a high resistance connection. This would result in low voltage, but not zero. Check it with an ohm meter, unless it is several hundred ohms you should get something. Another possibility is that you’ve shorted something to ground. In that case continuity will be good, but the short will always force the voltage to zero.
    "Never attribute to malice that which can be adequately explained by stupidity."

    "Any sufficiently advanced incompetence is indistinguishable from malice."

  3. #3
    Hammerhead Shark
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    I'm also guessing a short but you would have smelled it by now..
    perhaps it's not your connector.
    boo! bah!

  4. #4
    White Shark Moderator Moridin's Avatar
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    Not necessarily. The PS may be smart enough to look for shorts before putting any power on the line, so it doesn't blow up. In any case you will only smell something if there is burning or arching, and you don't automatically have either of these.
    "Never attribute to malice that which can be adequately explained by stupidity."

    "Any sufficiently advanced incompetence is indistinguishable from malice."

  5. #5
    Catfish gameboy1234's Avatar
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    How are you testing? It could be that a power supply detects that there is no load and shuts off, giving you no voltage when you test for it.

    Please give a few more details. Maybe even some ascii art and indicate your test points.

    Code:
    +-----------+  t.p. A   wire harness  t.p. B      load
    | Power     |----*----------------------*-------/\/\/\/\-+
    | Supply    |----*----------------------*----------------+
    +-----------+
    Test voltage at test point A. If good move on, if not, then your PS is not outputting any voltage. Mighe be a short in the harness that has caused the PS to shut off. Try it with just the load. If it doesn't work with just the load, the your load is bad, or the PS is bad.

    Test voltage at test point B. If not good, then you have a break in the wire harness.

    Give volts and current for PS if you want help with calculating the loads.

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