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Thread: chasing a short

  1. 8th December 2012, 09:18 AM #1
    wozapinin's Avatar
    wozapinin
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    chasing a short

    G'day, I have an electrical short in my defender and seek advice. When I first bought the vehicle a month ago I was told of the issue. Whenever the headlights were flashed (like saying hello flash) the fuse would blow. I pulled the steering wheel and shroud off to find a live connector floating around and shorting. I replaced said connector and all sweet for a week. Now there is a constant short and the (ceramic) fuse blows as soon as replaced with none of the items associated with the fuse being used (headlight flash, horn, interior lights, stereo).
    I first individually disconnected each item, as well as connecters under steering wheel (indicator stalk etc) but fuse still blew.
    As an experiment (really hoping to smell see smoke somewhere other than the fuse) i shorted the fuse terminal with a short piece of wire, lots of smoke at wire, not recommended, didn't help.
    Today i used a test light to determine positive side of the fuse holder. then I used a fuse-able link, (with glass fuse as i have lots to kill) and the test light on the opposite side and attached it to positive battery terminal. I was hoping this would show me the feed was the problem but seems its not as items still didn't work. Having said this the fuse didn't blow either, but the test light glowed brighter when operating all associated electrical items.
    Can someone advise me on another test or is it dash apart to find the bare wire/short...hope my jibberish makes sense...cheers.
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  2. 8th December 2012, 10:56 AM #2
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    The best short circuit detector is a headlamp globe or similar of around 100-130 watts wired across the fuse contacts. Wriggle like fury and observe if the globe is bright or not. Saves on repeat fuse blowing and shows the very instant a connection changes its short circuittyness.
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  3. 8th December 2012, 11:30 AM #3
    Hoges
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    In past exercises such as this I have found it useful to map out the circuits with a 'texta' marker on a piece of "butcher's paper" to keep track of what I've tested and under what conditions (connected/disconnected etc) that helps narrow down possibilities. You mentioned a "floating" connecter...could there be other bits floating arounbd as well?

    If you "disconnect" all the items, does the ceramic fuse still blow?

    I'd turn off all the items then disconnect them. Then take bee utey's advice and use a large wattage globe or glass fuse but in parallel (piggy back) across the ceramic resistor. Then reconnect each of the "items" one by one and see which one causes the glass fuse to blow /light the bulb. They should not be drawing any current if they're switched off, so that particular circuit is causing the short I'd have thought... without seeing it...etc etc good luck with it!
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  4. 11th December 2012, 07:33 AM #4
    zwitter
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    I too recommend the lightbulb across the fuse, i use a 45w sealed beam. Then you wiggle all he loom. I am lucky enough to have a clamp meter at work i can borrow and just clamp around the loom at various points to see the current flowing. You just follow the loom and measure until the current no longer flows and the fault is between that and the previous point.

    I think your smoke test may have done harm and you may be better off cutting the loom and bridging the shorted section. I have done this to my horn wire and another wire behind the dash. Just cut in a spot you can get to to join it again.

    I had great problems with rear lights and trailer socket so bought new bullet connectors and joiners and replaced all of them and sealed all the water leaks. Took a whole day but perfect since! And don't forget the earth points.

    James

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  5. 11th December 2012, 12:15 PM #5
    mike 90 RR Guest
    Quote Originally Posted by wozapinin View Post
    Whenever the headlights were flashed (like saying hello flash) the fuse would blow
    Unplug the headlights and test .... ......

    A faulty headlight or a bad headlight plug connection (pins) will cause resistance and heat / blow the fuse.
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  6. 12th December 2012, 12:35 PM #6
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