> From:    Jeffrey Vickers <jeff@VICKERSDESIGN.COM>
> Date:    Mon, 16 Apr 2007 11:32:08 -0700
>
> Anyone have a diagram for wiring dual horns with two terminals each
> horn?

Mike Collum posted a good one.  In addition to what he said...

Make sure the wires on 85 and 86 are hooked up the way he shows them -
power to 86, ground to 85.  The reason this is important is that some
relays have a diode in parallel with the coil, and the diode is
sensitive to correct polarity.

If your relay does have a diode, and you swap the connections to 85 and
86 around, then you'll most likely blow the fuse in that circuit (the
10 A fuse at the upper left of Mike's diagram.)  If you don't blow the
fuse, you might blow the diode.  If the diode fails open circuit, OK -
you simply have a working, diode-less relay.  If the diode fails short
circuit, then the relay won't work.

Again, not all relays have this.  Some have nothing, and some have a
resistor, which doesn't care about polarity.  The diode and/or resistor
are there to short out the spike which occurs when the relay switches
off.  When everything was done with mechanical switches, the spikes
didn't much matter.  When the relays started getting switched by
transistors, the spikes started to matter a lot.

I agree that if the horn terminals aren't marked, then the polarity
probably doesn't matter.

Where does the ground wire from the horns go?  Are you sure it's making
solid contact to the body of the van?

It can be helpful to test things in stages.  Pull the wires off of 30
and 87 on the relay.  Turn on the ignition and press the horn button -
the relay should click.  If the relay doesn't click, then there's a
problem with the horn button, relay, 10 A fuse (in Mike's diagram), or
wiring between these things.

If the relay clicks OK, grab the wires that you pulled off of 30 and 87.
Hold them BY THE INSULATION about an inch back from the terminals.
Touch the terminals together and the horns should sound.  If this
doesn't work, there's a problem with the horns themselves, the 15 A fuse
(in Mike's diagram), or the wiring between these things.

Holding the horn wires by the insulation is important because the horns
contain coils of wire as well and will also generate a spike when they
are shut off.  This spike is probably not as dangerous as sticking your
fingers into a wall outlet, but it will get your attention if you're
touching the wire terminals.  Ask me how I know.  :)

I hope this helps!

Matt Roberds