Irony
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 posted on 25/4/13 at 09:29 PM |
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Wiring fault found - unexpected continuity
Thought I just finished my indicator/hazard/dip/main lighting and I was tidying up the wiring when I came across three wires I didn't know what
they were for. They were the looms original flasher relay wires which I haven't used. The battery is disconnected at this point. In
identifying the three I happened to put a multimeter across an earth wire and positive wire. To my surprise I got continuity. I disconnected a
headlight and put multimeter across the headlight feed and the earth, continuity again. Disconnected a indicator, same result. I thought maybe I have
wired something wrong. So I reconnected the battery expecting a short, none came. Everything works okay? Am I being stupid?
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stevebubs
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| posted on 25/4/13 at 10:43 PM |
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Could the disconnected positive strap to the battery have been touching something that was earthed??
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snapper
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| posted on 26/4/13 at 06:00 AM |
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Switched earth systems can give this
i.e. +12V to light returns through earth wire to switch, switch goes to ground when switched
I eat to survive
I drink to forget
I breath to pi55 my ex wife off (and now my ex partner)
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Irony
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| posted on 26/4/13 at 07:19 AM |
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I check the strap to the battery so it wasn't touching - or I thought I did. I just don't understand. Surely if I have a short or I have
connected something wrong I should get sparks, a blown fuse or even a fire!!!!!!!!!!
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Stott
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| posted on 26/4/13 at 08:24 AM |
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If the positive you tested is linked to others then you may have measured a relay coil or even several such as the ignition on relay and fuel pump
relay etc.
Several of these in parallel will give a reading of almost short to earth. The only way to prove it would be to know the wiring scheme exactly and
disconnect the positive at its end and prove the cabling but if it was working before and it works now you probably haven't got much to worry
about providing its all fused correctly.
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scimjim
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| posted on 26/4/13 at 10:47 AM |
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surely the bulbs will show continuity to ground on both sides when switched off - they only produce heat and light (a controlled short circuit) when
you connect them to the battery.
so the +ve lead on your disconnected bulb holder is joined to the bulb on the other side (same supply from relay) - which is connected (via the
filament) to ground?
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Irony
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| posted on 30/4/13 at 11:28 AM |
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Sorted it.
I set the multimeter up for continuity and connected it in the place of a headlight. Whilst the constant tone was droning out I started moving the
loom around looking for loose connections. When that failed I started unplugging stuff. When I got to the dashing warning light display pod and
pulled it continuity was broken and the tone stopped. I plugged it back in and started removing each bulb in turn. The full beam warning lamp was
faulty and when pulled it out the tone stopped and I replaced it with a spare. No more problems.
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