Date: Thu, 22 Jul 2010 21:02:21 -0700
Reply-To: Robert Fisher <garciasghostvw@GMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Robert Fisher <garciasghostvw@GMAIL.COM>
Subject: Re: A/C Wiring/electrical help (pic)
In-Reply-To: <AANLkTinHTQGMI40FED9e_IjroC_4cKp_Q-3vlbL7fugM@mail.gmail.com>
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Well that'll get me started... I was thinking I'd pull and test each relay
first.
I guess I should've made it more clear that part of the link (I think there
were two strips) did indeed melt through; that pic is from after I put it
back together somewhat.
Thanks!
Cya,
Robert
On Jul 22, 2010 8:41 PM, "David Beierl" <dbeierl@attglobal.net> wrote:
At 09:48 PM 7/22/2010 Thursday, Robert Fisher wrote:
>
> http://picasaweb.google.com/garciasghostvw/...
That's a classic example of a high-resistance connection on the end that
melted. You can see that the link itself hasn't even had to breathe hard.
However I would expect given the photo that it would still work in this
condition, just that the far end would continue to get hot until the poor
connection was found and fixed. Notice that the sleeve on the crimp fitting
isn't melted, so that pretty much limits it to the actual connection between
screw and terminal and the link itself.
> Given the condition of the link I was thinking I might replace it with
> something like this:
>
...
I can't see any reason not, with the caveat that all these high-current
circuits need pristine connections or localized heating will cause damage.
That includes the connection between fuse and socket -- that's perhaps why
the existing link is bolted on instead of plugged in. I have had an 80-amp
ATC-type fuse (in-line in an inverter supply circuit) melt one side of the
socket (like the one you pointed to but perhaps larger) and seriously
distort the plastic of the fuse itself, exactly as your link did and for the
same reason.
> The thing is that I don't know if something like that is appropriate
> compared to the character...
I think it's fair to say that automotive fuses in general are slow-blow.
That doesn't necessarily include the small glass fuses for low-draw
electronics. A fifty-amp ATC fuse is not going to be a fast-blow.
> Secondly, does anybody know of a systematic approach to troubleshooting
the
> A/C electrical sys...
Robert, I haven't studied the A/C circuitry (since I don't have one) and I
don't plan to do it tonight, although I'm willing to work through it with
you when you run into problems. I definitely would suggest that you copy
the schematic, get some colored pencils and read my wiki article on figuring
out schematics. Holler when you get stumped.
> It has a ton of relays, for one thing, and I'm not
> sure how one would test those.
You test them by pulling them out, energizing and de-energizing the 86/85
terminals and checking for correct continuity on the other terminals as
shown on the schematic. If it's a simple four-terminal relay then you
should have continuity between 30 and 87 when the relay is energized, and
not otherwise. You should be able to hear the click as the relay pulls in.
The continuity buzzer on many multimeters is not sufficient; a better way
is with battery and a stoplight bulb that will actually pull some current
through the relay contacts. But at minimum you need to see zero or at
absolute most maybe a tenth of an ohm with a meter. Seriously, rig up the
stoplight bulb, that will draw a couple amps or so and prove that the
contacts will actually pass current. Measure the voltage drop across the
contacts while the bulb is lit -- the closer to zero the better. A hundred
millivolts with that load I'd consider marginal at best.
> I'm hoping to avoid the brute-force approach
> of following the current from the fuse block bac...
With the caveat that you'll be following the voltage and not the current,
I'd suggest that doing exactly that is not at all brute-force but (in
combination with the schematic) the proper and intelligent way to
troubleshoot any Vanagon electrical fault. Replacing stuff at random is
called "shotgunning" and is otherwise known as the expensive way to (maybe)
fix a problem -- not as bad as running at the coal fyce with yer 'ead, but
more in line with scrabbling at it wi' yer bare 'ands. I say (maybe)
because often the problem is in the wiring.
Help? : /
>
Is that at least a crumb?
Yours,
David