Date: Mon, 24 Oct 2011 12:49:03 -0700
Reply-To: courtney hook <courtneyhook@SHAW.CA>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: courtney hook <courtneyhook@SHAW.CA>
Subject: Re: [WetWesties] Multimeter help UPDATE-77 Westy
In-Reply-To: <4ea54b79.f05c340a.5f6f.ffff8e31@mx.google.com>
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Thanks for the info David, I will try this when I get home from work tonight. You are correct; my clumsy writing style made it seem like I had both cables off, but I did not. I merely removed the +ve cable for a moment to disconnect the other smaller +12v wires that ran to my battery charger and the diagnostic plug. Appreciate any further help you and all the others are providing.
Regards,
Courtney
----- Original Message -----
From: David Beierl <dbeierl@attglobal.net>
Date: Monday, October 24, 2011 4:26 am
Subject: Re: [WetWesties] Multimeter help UPDATE-77 Westy
To: Courtney Hook <courtneyhook@shaw.ca>
Cc: wetwesties <wetwesties@yahoogroups.com>, type2 <type2@type2.com>, vanagon list <vanagon@gerry.vanagon.com>
> At 03:52 PM 10/22/2011, Courtney Hook wrote:
> >OK, so something is def. not good here. I wasn't getting
> anywhere with the multimeter, so I tried the other method which
> someone forwarded to me, I put a 12v light between the negative
> cable and negative post with everything turned off. The light
> came on. This is supposed to indicate a current draw. I then
> proceeded to remove the fuses one by one to see which circuit
> the light went out on. It didn't go out at all. I even removed
> the backup, gas heater, and 2 other 30 amp fuses on my Westy.
> Light still stayed on. I took off the positive cable and removed
> the red + wire to the VW diagnostic plug at the back thinking it
> might be grounding, along with the other .... The light
> still stayed on.
>
> I'm assuming a typo here. Reading the last two sentences
> as written, you have the battery pos connected to nothing, the
> battery neg connected to chassis ground through a test light,
> and the light is lit. That's not possible. Given
> that assumption, you can use current tracking to find the leak.
>
> Hook the battery back up, leave the fuses removed. Add a
> long wire to your multimeter + lead and connect it to battery
> positive. Now set the meter to the 200 mv or lower scale
> and start probing along your still-live wires (with a sewing
> needle if necessary), following the millivolt drops which will
> gradually increase along a particular wire until you get to the
> fault. You will only find drops on wires where current is
> flowing, so when you get to a branch point find the branch where
> the readings continue to increase as you follow the wire out.
>
> You'll need good contact on the meter probes, may need to polish
> them to avoid odd/misleading readings.
>
> If the "sneak current" is enough to light a test light bulb I
> think a 200 mv scale will probably let you trace it; but a more
> sensitive meter would make it much easier as you wouldn't have
> to travel so far along a wire to get a noticeable drop.
>
> If the sneak current is 200 mA, then you'd get about a 2.5 mV
> drop along a meter of 1.5 mm^2 wire (fat 16 ga), but would need
> four meters of 6 mm^2 (fat 10 ga) wire to get the same
> drop. This would be a lot easier to trace with a 20 mV
> scale where you could read fractions of a millivolt. I
> have a meter with a four-digit display that reads to .001
> mV. You probably don't, but the more sensitive meter you
> can find, the easier the job will be.
>
> Yours,
> David
>
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