Date:         Wed, 21 Mar 2001 17:11:12 -0500
Reply-To:     Michael Sullivan <sullivan@OPENMARKET.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Michael Sullivan <sullivan@OPENMARKET.COM>
Subject:      Re: horns that don't sound so lame
Content-Type: text/plain; charset="iso-8859-1"

Dear List,

For a look at what VW had in mind when they installed dual horns an a
factory option in Europe, consult the following diagram:

http://www.haywood-sullivan.com/vanagon/dual_horns_wiring_diagram.gif

You will notice that they relay the ground!!!
Wierd German engineering indeed!

Enjoy,
MJS



-----Original Message-----
From: Scott D Foss [mailto:turbovans@JUNO.COM]
Sent: Wednesday, March 21, 2001 4:34 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: horns that don't sound so lame


Tony,  RE  " internal horn relay "  :

page 97.64 Bentley book,
current track 53
shows the horn, and internal stuff,

but that little coil in the horn is the
coil of the horn, which is not really a relay.

A relay has a coil like that but what makes it
a relay is the coil energizes ( pulls - it's an elctromagnet )
contacts for another circuit.

thus providing what a relay does :
It isolates the switching function from
 the load function.

Withot  relays the ignition switch would have to be huge to carry the
starter motor current, for example.

a starter solenoid is  a perfect example of a relay,
it jumpers the two contacts which connect battery voltage to the starter
motor,
it also happens to pull the starter gear into engagement at the same
time, which is why a solenoid is so big for a relay.

You can see in current track 53 that power is supplied by fuse S 12 to
the horn on one side of the coil.
when ground is supplied to the other side of the
coil by the horn button the circuit is complete.

the way horns and buzzers work,
the contacts ( which are movable ) are normally kept closed by a spring -
the coil engergizes,
and it pulls the contacts apart, breaking the
circuit, but the springs pull the contacts back together
re-energizing the coil, which pulls the contacts apart,
over and over, thus the buzzer effect, or in the case of the horn, an
amplified buzzer thru the " horn " part of the horn.


you can see in the little drawing that the contacts are normally closed.
they don't show you that the coil pulls them into non-contact, but that's
how it works.

  scott