In our Vanagons, all the power for the headlights goes thru the headlight
switch from the battery, to the headlights.  The switch is the problem, as
it has too much resistence in it to the power, and when the happens, the
power to the lights is reduced by the switch.  The switch internals will
also tend to get hot when this happens, and the heat often makes the
situation worse.

  A relay, also called a contactor, is a remote control switch, it is a
heavy duty switch, that can pass high power, without getting hot, and
without power getting used up going thru it.
  It is remote control, becuase you will use an other "lower quality" switch
to remote control it to turn on or off.  The power needed to remotely turn
on or off your relay is only a very small amount, hence you can use a cheap
light duty switch to activate the relay.

  The relay will allow more power to pass.

  The Vanagon headlight switch is a "cheap" light duty swithc, and really is
not a good choice for running the headlights.  Install the relay for the
headlights, and use the stock switch to remote control the relay, and you
will have brighter stock lights, be able to install higher power aftermarket
lights (which would kill the stock swith quickly if no relay), and your
stock switch will last maybe longer than you r Vanagon.

dave
----- Original Message -----
From: "The Shaws" <mindthegap01@COMCAST.NET>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Wednesday, September 15, 2004 9:47 PM
Subject: What does a relay do?

> I hope you experts don't mind me asking this question but I have read
about
> this several times on the list and would like to understand the idea.
>
> I have read 2 relay situations:
>
> 1. Installing headlights with greater intensity. Use a relay...
>
> 2. Install a relay in the fan switch to prevent the switch from burning
> out...
>
> So my understanding is that the addition of lights with a greater energy
> demand draws more power than the wires can handle... so what does the
relay
> do?
>
> thanks
>
> peter
>