Looking at Bentley again, it does claim that these #s are mm diameter,
or AWG (page 97.4 "How to read wiring diagram").   Unless the chart on http://en.wikipedia.org/wiki/American_wire_gauge
  is wrong, there's no way that these match up -- 2.5 and 6 are
clearly not AWG.

The  "2.5" is about right if it's mm diameter: that would be just a
hair under 10 gauge.  However the "6.0" would then be between a 2 and
3 gauge which is clearly not true.

Very odd -- is this a Bentley error, or a manufactureing one, e.g. the
specs called for a "6.0" wire but something smaller was actually
built?   (page 97.62)

On Jul 12, 2008, at 2:47 AM, Sean B. wrote:

> Michael,
>
> IIRC the 2.5 and 6.0 are supposed to represent millimeters. However,
> that measurement does not include the insulation. I'll have to check
> my wiring diagrams to see how the power is distributed, but that
> does sound like something VW would do.
>
> Michael Diehr wrote:
>> [responding to a very old thread]
>> I was having voltage problems in my 85 westy -- freeway driving with
>> AC and headlights on was causing battery to drain, not charge --
>> replaced the alternator but that really didn't fix it.
>> Finally took the advice and checked out the power wires from the
>> alternator -- sure enough, inside the wiring box they were totally
>> cooked.   Investigated some more, and realize just how crazy the
>> german engineering was.   Instead of putting in a single beefy wire
>> from the alternator to the starter, they put in two(!) on a single
>> crimp, then run these from the alternator in a spaghetti like path
>> all
>> the way to the left side where they meet another wire, which then
>> reverses the course and ends up at the alternator.
>> Bently lists the 2 from the alternator as "2.5" which junction with
>> the one returning to the starter which is listed as "6.0".  If I'm
>> reading the diagram correctly, the entire electrical system passes
>> through this junction to the rest of the van.    I don't know what
>> 2.5
>> and 6.0 represent  -- doesn't seem to be mm, mm squared, gague, or
>> amps.
>> In any case, I'm replacing the two 2.5s with an 8 gauge and soldering
>> the connections, which should help a bit.
>> Anyone know if the existing "6.0" wire from the junction to the
>> starter is indeed what feeds the entire system?  Eyeballing it it
>> looks like about an 8 gauge as well.
>> I would also echo mark's recommendation that 85 and earlier owners
>> check the junction box -- it just takes a minute, no tools required.
>> On Aug 6, 2007, at 3:04 PM, Mark Drillock wrote:
>>> If I were you I would first examine very closely the 2 red power
>>> wires
>>> from the alternator and also follow them to their other ends. I have
>>> seen more of these cooked than you would think. They are often
>>> cooked at
>>> the ends hidden inside the engine compartment wiring box. VW
>>> increased
>>> the current capacity of this circuit by 250% in later years and that
>>> is
>>> what I would do on yours. Run a new 8 gauge wire from the alternator
>>> to
>>> the starter motor, using soldered on wire ends made for 8 gauge wire
>>> and
>>> 5/16 bolt hole. This will likely cure most of your problem but if
>>> you
>>> measure the voltages at the starter motor lug first you will know
>>> how
>>> much of the drop is there. Test unloaded and loaded, as before.
>>> [...]
>>> Mark
>
> --
> Sean B.
> '90 V'gon 2.0 ABA (under construction)
> '82 airsucker V'gon, "The Rat's Nest"
> '87 8v GTI, '91 Jetta
> http://www.vgonman.com
>