Difference between revisions of "Solving wiring diagrams -- a technique"

From Vanagon Wiki
Jump to navigation Jump to search
(Created page with 'David Bierl: In understanding Vanagon (or any other) wiring diagrams there is a not-so-little trick that will make it vastly easier to figure out what's really going on in a cir…')
 
(deleting until I get permission for content)
Line 1: Line 1:
David Bierl:
+
(deleted the content until I can get permission from the original posters)
 
 
In understanding Vanagon (or any other) wiring diagrams there is a
 
not-so-little trick that will make it vastly easier to figure out
 
what's really going on in a circuit.  Before you can do this of
 
course you have to be familiar with Bentley 97.3-97.6. so the
 
diagrams make any sense at all.
 
 
 
The trick is this:  First copy the page in question so you won't
 
wreck the original if you mess up somewhere.  Get yourself an
 
assortment of colored pencils, at least five or six including brown
 
and red.  Then take a look at
 
http://picasaweb.google.com/dbeierl/FiguringOutVanagonWiringDiagrams#
 
for a working example of how it's done.  You may want to keep it open
 
to refer to or make a color print of it to use the first time or two
 
you do this.
 
 
 
Start by locating the grounds.  Since this is a physical schematic
 
some of them may originate far away from where you're looking even if
 
it would be easier to understand if they simply drew all of them
 
straight down to line at the bottom line of the page, which is
 
chassis ground.  Every terminal labeled as 31 is a ground.  Every
 
ground you find, draw  a brown line next to the wiring for its whole
 
length. For switched grounds I recommend a dashed line instead of
 
solid upstream of the switch.
 
 
 
Then look for the +12 supply wires and color them red.  You may well
 
want to use different colors for unswitched (terminal 30), switched
 
by ignition (terminal 15),  and switched by the load reduction relay
 
(X-terminal on ignition switch operates it; power upstream is 30 at
 
the relay, downstream (switched) is 87 like all relay
 
outputs.  Again, power that's switched downstream should use a dashed
 
line downstream of the switch.
 
 
 
Now pick a wire and figure out what it does.  Follow it off the page
 
if necessary and label where it goes on your drawing.  If you can't
 
figure it out, pick another wire.  As soon as you know what it does,
 
label it as such then pick a color for it and draw solid or dashed
 
line as appropriate.  If a single wire does multiple things, as in
 
the circuit from 53e at the motor up to the switch, down to the relay
 
and thence to the motor 53 terminal, use multiple solid or dashed
 
lines as appropriate (Note: the pink wire should be dotted for its
 
entire length and there should also be a brown dotted line for the
 
whole length of that circuit.  Can you discover why?  Answers on
 
request.  Hint: I missed one of the functions of the auto-park switch).
 
 
 
Keep on doing this for wire after wire until you understand them all
 
(or are certain you understand enough of them, which may or may not
 
be true).  Each wire you figure out makes the rest easier, and the
 
colored lines take away the visual anonymity of Joe Random
 
Black-line-on-the-page.  Now you can follow the circuit around and
 
find out where a particular problem might (or must) lie as well as
 
where it cannot.
 
 
 
This is the second time I figured out this particular wiper
 
circuit.  The first time I forgot this trick I learned thirty years
 
ago, and it took me over an hour.  This time I remembered, and it
 
took about ten minutes after I found the colored pencils and
 
photographed the page.  And I was easily (but not in ten minutes)
 
able to establish that the relay cannot possibly be correct as drawn
 
(since at some point it would hook +12 directly to ground) and how it
 
would actually have to be (which happens to coincide with the diagram
 
molded into the side of the actual 19 relay, but I didn't know that
 
at the time.  I definitely did *not* figure that part out the other time.
 
 
 
Yours,
 
David
 
 
 
Robert Keezer adds:
 
 
 
This is an idea I had 15 years ago when I was installing Digifant 2 and later Motronic fuel injection wiring in my 82 Westfalia ,with one additional trick-
 
make the copies larger than the Bentley, making them easier to read.
 
 
The circuit tracks are very close on top of the page, and I mixed up the 1 wire with the 15 wire and fried the computer before I ever got it started.
 
 
Colored marking pens also work well. Once you learn these diagrams, you can troubleshoot any circuit easily, or do a conversion. Many of the color codes for Vanagon are the same for Jetta , Golf etc.
 
 
 
[[Category:diagnostic_tips]][[category:understanding_bentley]]
 

Revision as of 08:45, 7 May 2010

(deleted the content until I can get permission from the original posters)