Date:         Fri, 4 Oct 2002 17:22:24 -0700
Reply-To:     Brent Christensen <sbsyncro@HOTMAIL.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Brent Christensen <sbsyncro@HOTMAIL.COM>
Subject:      Sanity Check - Wire gauge for wiring SA headlights
Comments: To: Syncro@yahoogroups.com
Content-Type: text/plain; charset="iso-8859-1"

I am planning out the wiring for my new e-code headlights, and I wanted to run a sanity check for the gauge wires I plan to use.

I will be running 100/80 H4 bulbs plus the 55w driving lights.  I will be using relays to hook everything up, of course!

Total Amperage draw:

High beams ~8.5 amps x 2
Low beams ~6.7 amps x 2
Driving lights ~ 4.6 amps x 2

Based on the wiring tables I can find, 14 awg wire is duty rated to 17 amps for stranded wire at up to 135 degrees ambient temperature.  Since the lamps will each be wired separately from the relays, I am assuming that I can use the following wire gauges:

8 awg as a "feed" from the battery to the fuse block.
10 awg from the fuse block to the relays
14 awg from each relay terminal to the individual lamps.

Can anyone more expert than me confirm or dispute my findings?  It tends to support the wimpy 14 awg wiring that VW uses from the factory.   By the way, at 8.5 amps current draw, the voltage drop from 12.5 volts through six feet of wire are as follows:

10 - 5.2%  (or 11.9 volts)
12 - 8.3% (or 11.5 volts)
14 - 13.1% (or 10.9 volts)

Maybe this is a bigger reason to use 10 awg wire to the brights and low beams than the actual rating of the wire...?

Brent Christensen
Santa Barbara, CA