Date: Thu, 21 Oct 1999 07:08:02 -0700
Reply-To: David Marshall <vanagon@VOLKSWAGEN.ORG>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: David Marshall <vanagon@VOLKSWAGEN.ORG>
Subject: Re: Headlight wiring harnesses and voltage drops
In-Reply-To: <Pine.SOL.3.96.991021070627.15711A-100000@yoda>
Content-Type: text/plain; charset="us-ascii"
Yes, keep runs short, run ground direct to the body to keep everything to a
minumum, but the run from the battery to the lights is what you have to
woorry about. Anything is an upgrade to the factory system that seems to
run circles in the dash. Changing just the ground should not make that
much difference unless everything was semi-corrorded at the factory
connection.
At 07:15 AM 21/10/1999 -0400, EMZ wrote:
> Dave,
> I have solved this problem by keeping the wire runs short, running
>the grounds, right to the body, and running an individual wire (14 AWG)to
>each light. Turns out that the grounds are most of the problem. Since I
>discovered this I have made just the ground change on seven other
>friends Vanagons, to witch everyone of the owners thought I did magic!
>These were all the original square head lights.
>
> Eric 86-VW4x4
> vw4x4@fyi.net 72-240z
> Pittsburgh, PA USA 1936-Chrysler
>
>
>On Wed, 20 Oct 1999, David Marshall wrote:
>
>> I am in the process of making the finishing touches to my prototype wiring
>> harness for installing high powered lamps in our Vanagons with out melting
>> our headlight switches.
>>
>> This kit will run a direct, fused, line to the positive terminal of the
>> battery and incorportate some some relays in a waterproof enclosure that
>> will be mounted behind the grille. The relay will be triggered from the
>> input from one of the original headlight plugs.
>>
>> What I am having problems with is what everyone will accept as a
>> satisfactory voltage loss across the harness. As we all know all
>> electrical devices have resistance. The more current we run through a
>> resister the more voltage drop we get. Lets get a little technical to
>> prove this point.
>>
>> Lets say there is 20ft of wire between the headlights and the battery and
>> we have gone crazy and installed 80/100W H4s and some 130W H4s in our
>> Vanagon for a total of 460W of power consumption on highbeams (much like my
>> Double Cab only there is 2x 150W for the rallye lights!).
>>
>> The electrical requirements for the lights would be:
>> Lights are rated at 460W at 13.5V. Meaning they require 34.074074A of
>> current ( I = P / V ). The resistance of these lights would be 0.396195
>> Ohms ( R = V / I )
>>
>> The 20ft of wire has some resistance we have to calculate into the system:
>> - 20ft of 14ga wire at 20C is 0.05050 Ohms
>> - 20ft of 12ga wire at 20C is 0.03176 Ohms
>> - 20ft of 10ga wire at 20C is 0.019978 Ohms
>> - 20ft of 8ga wire at 20C is 0.012564 Ohms
>> - 20ft of 6ga wire at 20C is 0.007902 Ohms
>>
>> Using 14 gauge wire the total resistance of the circuit would be .446695
Ohms
>> Using 10 gauge wire the total resistance of the circuit would be .416173
Ohms
>> Using 6 gauge wire the total resistance of the circuit would be .404097
Ohms
>>
>> The total current consumption for the curcuit would be as follows ( I = V /
>> R ):
>> 14 gauge = 30.221963 A
>> 10 gauge = 32.438433 A
>> 6 gauge = 33.407820 A
>>
>> The voltage drop after the 20ft run of wire would be ( V = I R ):
>> 14ga = 1.526209 V or 11.973791 V for the lights
>> 10ga = 0.648055 V or 12.851945 V for the lights
>> 6ga = 0.263988 V or 13.236012 V for the lights
>>
>> Leaving us with less light output ( P = V I ):
>> 6ga = 442W or 4% less
>> 10ga = 417W or 9% less
>> 14ga = 362W or 21% less
>>
>> Now, we have a compromise between cost, ease of installation and light
>> output. 6ga wire is what the VW factory uses for your battery's ground
>> connection. It is quite expensive, especially if you get the easy to bend,
>> mega stranded stuff. 10 gauge is quite a bit cheaper but you are getting
>> up to 10% light loss especially when the tempratures go up. 14 gauge is
>> just too thin and would get very hot (i.e. possible fire) if used over a
>> long period of time. An alternative would be to run two wires to the
>> lights thus cutting the resistance values in half, this however would add
>> cost to the kit.
>>
>> If you were going to install this wiring harness, what wire gauge would you
>> want to see used. How much would you want to be willing to pay to a "cut
>> no wires" "plug and play" wiring harness like this? One wire or two
>> running to the battery?
>>
>> Thanks for the input!
>>
>>
>>
>> -- David Marshall - - Quesnel, BC, Canada --
>> -- 78 VW Rabbit, 80 VW Caddy, 84 VW Westie, 85 VW Cabriolet --
>> -- 87 Audi 5000 Quattro, 88 2.0L VW Syncro Double Cab --
>> -- David's Volkswagen Home Page http://www.volkswagen.org --
>> -- Fast Forward Autobahn Sport Tuning http://www.fastforward.ca --
>> -- david@volkswagen.org (pmail) or vanagon@volkswagen.org (list) --
>>
>
>
>
-- David Marshall - - Quesnel, BC, Canada --
-- 78 VW Rabbit, 80 VW Caddy, 84 VW Westie, 85 VW Cabriolet --
-- 87 Audi 5000 Quattro, 88 2.0L VW Syncro Double Cab --
-- David's Volkswagen Home Page http://www.volkswagen.org --
-- Fast Forward Autobahn Sport Tuning http://www.fastforward.ca --
-- david@volkswagen.org (pmail) or vanagon@volkswagen.org (list) --
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