Date:         Fri, 2 Oct 2009 09:56:35 -0700
Reply-To:     Al Knoll <anasasi@GMAIL.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Al Knoll <anasasi@GMAIL.COM>
Subject:      Re: No High Beams
Comments: To: Rocket J Squirrel <camping.elliott@gmail.com>
In-Reply-To:  <4AC53BFE.7070504@gmail.com>
Content-Type: text/plain; charset=ISO-8859-1

On 10/1/09, Rocket J Squirrel <camping.elliott@gmail.com> wrote:
>
> Yes -- the aging of the electrical connections in the van will lead to
> increased resistance and reduced current. Spots where the resistance is
> high will be the warmer spots as heating is proportional to current and
> resistance.


So true but the power dissipation (heat) is proportional to the square of
the current.  With a ~10A current and a 0.1 ohm resistance the
I**2 R gives us 100 x 0.1 or 10W.  But I learnt my circuit stuff back in the
60s and who knows what has changed since then.

Pensionerd.

--
> Mike "Rocket J Squirrel" Elliott
> 84 Westfalia: Mellow Yellow ("The Electrical Banana")
> 74 Westrailia: (Ladybug Trailer company, San Juan Capistrano, Calif.)
> Bend, OR
> KG6RCR
>
>
>
> On 10/1/2009 3:35 PM Kim Brennan wrote:
>
> Electrical circuits used in our Vanagons use copper wiring, with
>> connectors usually of brass. Both copper and brass as subject to
>> corrision (especially in the presence of water). As they corrode, less
>> metal is available to carry the electrical current (leading to higher
>> resistance in the circuit.) Higher resistance means that some of the
>> current goes into generating heat. Heat on wiring can lead to melting
>> of the insulation. This in turn can expose more of the wiring to
>> corrosion....
>>
>> All of this takes time (and usually water).
>>
>> I'm not positive as to what metal the fuses are made of, tin, aluminum
>> or something. I've seen surface corrosion on them as well.
>>
>> With aluminum (and I believe tin), the surface oxidation tends to
>> prevent further corrosion. This is not true in the case of copper or
>> brass. However, aluminum oxide is a very poor conductor of electricity
>> and has a fairly high resistance (and remember that thing above where
>> resistance leads to heat?)
>>
>>
>> On Sep 30, 2009, at 1:16 AM, Rocket J Squirrel wrote:
>>
>> (If someone wants to chime in here with a description of how
>>> electrical
>>> bits in something simple like the brake light circuit can age in
>>> such a
>>> way that the on current is greater in an older van than in a new
>>> one, it
>>> would be helpful.)
>>>
>>
>>