Relay tail lights?

[gforbess at attglobal.net (Gordon Forbess)]

On Sat, 4 Mar 2006 12:46:04 -0500, GGehrke <ggehrke@gmail.com> wrote:

>Has anyone relayed their tail lights?  I'm thinking running lights I
>probably will because I want to have pretty light wire running through
>to all the switches and such.
>I'm thinking brakes would be nice because I want those as bright as
>possible, but I'm thinking that relaying them is not good because of
>the delay of the relay.  Anyone have any experience or thoughts?
>How about turn signals?  Is that even possible?  or just completely unnecessary?
>
>This is all in context of a complete rewire from scratch, btw, so I
>can do anything I want.  I want to overengineer this car to be as
>ridiculously stout as possible.

Electrical current flows at a speed approaching the speed of light and
the typical Bosch relay is close to instant, so I doubt you'd have the
problem you fear in the brake lights.  

Building a circuit that uses the switch wire as a trigger (as opposed
to running full current through it) is a good idea.  The other parts
of it are locating the relay close to the point that the current will
be used and having a strong source of +12 volts near that point.
Headlights are a natural, since (normally) you have the trigger wire
(the original headlight wires) and a source for a strong +12 volts
(the battery) located near where the bulbs are.  Just add the relay in
that general area, run larger supply wires from it to the bulbs, and
you're in business.

http://pws.prserv.net/gforbess/scirocco/relay.jpg

To get the most out of a relayed brake light circuit, you should have
a strong +12 volts in the trunk that is fed to the bulbs when the
relay (located there) is triggered.  You could run a large wire from
the battery (fused, of course) to the trunk area to do this.  Whether
it actually brightens the bulbs when you're done spending the time and
money to do it, I can't say.  But the idea is sound and worth a test,
anyway.  (Heck, I might try it with a spare relay I've got by just
ghetto rigging one side that way for a comparison).

As far as relaying the running lights, the problem with that is they
(particularly on my 75 mk1) are spread all over the car.  You could do
it, but I think it would require either lots of larger wire or several
relays to make any real difference.

Gordon
75 Mk I/Drake 1.9
http://pws.prserv.net/gforbess/scirocco/scirocco.htm