Stuart,
  I'm afraid you are too far out on your limb.  Your basic starting point
that any device will use a fixed amount of power is incorrect.
That makes the rest of your argument and conclusions false.
  I am wondering where you came up with that premise.

Larry A.

On Sat, Dec 21, 2013 at 7:43 PM, Stuart <ve3smf@yahoo.com> wrote:

> OK, I am willing to go out on the limb for this one.....
>
> First some background.  Any device such as headlights, heater fans,
> blowers, etc will draw a fixed amount or power.  P=I*E where Power in watts
> = Current times Voltage.  The problem is, when voltage drops, the device
> still draws the same power, and the amount of current required (ampre) will
> go up.
> ref: http://www.sengpielaudio.com/calculator-ohm.htm
>
> The second issue is the ability of any wire to conduct and not melt
> depends on the ampres, not on the voltage.  A given wire can carry high
> voltage, and low ampre, but not high ampres, at low voltage.
> ref: http://www.engineeringtoolbox.com/amps-wire-gauge-d_730.html
>
> In the case where either a battery in a vehicle is failing  and/or the
> alternator is failing, under high power load (such as headlights on high
> beam, heater fan going and air circulation fan going), the voltage will
> drop.  When an alternator fails, it will still be possible for a vehicle to
> drive for a while, until the voltage from the battery drops to the point
> that the coil will not provide sufficient spark to the engine.  The other
> issue is the electrical circuits through the ignition switch are designed
> to sustain a maximiun current (ampre) flow at 13.8 VDC.  When the voltage
> in the system goes down, the ampres go up (P=I*E).  With the higher current
> flow, and the inherit internal resistance of the wiring, the wires and the
> switch will heat to the point that the copper and switch will melt.
>
> In the case of a battery and/or alternator failure (cause) under high
> power demands, you will get circuit wire and switch failure (sysmptoms).
>
> In this case, I hope that several fuses melted before damage happend to
> the wires.  Tracing and replacing burnt wire harness is not fun.  The
> ignition switch may have also failed, but has been pointed out, this is
> easy to replace.  As far as the actual cause of the failure, I would look
> at both the battery and the alternator.  This will likely be a multi-point
> failure.
>
> In terms of monitoring the state of health of a vehicle electrical system,
> one of those cigarette plug in voltage monitors would have given diagnostic
> information as the system was failing.  The fact that the high beams were
> required to be on, as well as the heater fan and  front fan pushed the
> system over the edge.  The unit that I have will monitor the battery
> voltage when every thing is turned off, and the system (alternator voltage)
> when everything is running.  This is very valuable information.  The best
> system would look at both the battery and the alternator at the same time.
> On Youtube is a project that was done with a focus on the Arduino-based
> power monitoring system.
>
>  http://www.youtube.com/watch?v=0gS6RaVO8po
>
> I hope things work out, and you can share the final results.
>
> Stuart
> 86 Vanagon GL 2.1L
>
>
>
> ________________________________
> From: Ken Wilford <kenwilfy@COMCAST.NET>
> To: vanagon@GERRY.VANAGON.COM
> Sent: Friday, December 20, 2013 10:27:03 AM
> Subject: Re: Van Dies while in motion
>
>
> Tony,
>
> Sounds like the ignition switch as Jim has stated.  Or it could be an
> alternator/battery issue or both.  I would get a new battery and a new
> ignition switch.  You can drop the lower column cover, unplug the old
> ignition switch from the harness and plug the new one into the harness
> without installing it.  Use a small screw driver to turn it in the slot
> that is on the side that is away from the plug just like you would be
> turning the key in the ignition normally.  If the van starts right up
> and is back to normal then that is the problem, get it home and install
> the new switch.  If not, install the new battery (group 41 from
> Wal-mart).  Now try starting it.  Even if the alternator is toast it
> should start up and be able to be driven for an hour before getting so
> low that it kills the engine again (try not to run any other lights or
> fans if you can help it).  Use a volt meter at the battery to see if the
> alternator is putting out.  It should be doing at least 13.5volts.  You
> may have to rev the engine above 2000 rpms to get it to kick in.
>
> Let us know what you find out.
>
> Ken Wilford
> John 3:16
> www.vanagain.com
>
> PS
> Welcome to the Vanagon List!
>
> On 12/20/2013 1:46 AM, Anthony Boscolo wrote:
> > Hi all,
> >
> > This is my first post so I will try to be as clear as possible. I have an
> > 1986 Syncro GL.
> > Driving up to the mountains tonight the head lights went out...about 20
> > seconds later the engine died...the key is stuck in the ignition and if i
> > turn it the dash lights (bat,ox, etc...) don't respond.  There is no
> noise
> > at all if I turn the key.
> >
> > At the time I had the rear heater on full, and was running the
> > high-beams...and I may have had the front heater/fan on as well.
> >
> > Any thoughts on what went wrong? fuse?  if so I can't figure out which
> one.
> >
> > In the meantime, the Van is on the side of the road on SR 410 just before
> > the turn up to crystal mt. If you see her, wish her good thoughts.
> >
> > Thanks for the help
> >
> > --
> > Anthony Boscolo | 206.794.1727 | abosail@gmail.com
> >
> >
> > -----
> > No virus found in this message.
> > Checked by AVG - www.avg.com
> > Version: 2014.0.4259 / Virus Database: 3658/6937 - Release Date: 12/20/13
>
> >
> >
>
> --
> Thanks,
> Ken Wilford
> John 3:16
> www.vanagain.com
> Phone: 856-327-4936
> Fax: 856-327-2242
>