Date:         Thu, 30 Oct 1997 16:09:08 -0400
Reply-To:     mark keller <kelphoto@BRIGHT.NET>
Sender:       Vanagon mailing list <Vanagon@Gerry.SDSC.EDU>
From:         mark keller <kelphoto@BRIGHT.NET>
Subject:      Re: Horn
Content-Type: text/plain; charset="us-ascii"

First I'm assuming, so please check, that your horn takes 12 Volts from the
fuse box, and then when you press the button, 12 volts  to the horn, from
your discription of events.  Some horns the hot wire is to the horn  and
the "button just grounds the horn.  Either way the advice is applicable,
just subsitute for your situation if different.

OK here goes. You need two electrical things to make da horn blow.

Voltage, and amperage.  Using a water in a garden hose as a model, voltage
relates to the diameter of the hose, or how much it is capable of holding
inside.  Amperage, relates to how much pressure, in this example water
pressure would represent amperage.

All electrical devices on a car have a volt and amp requirment. Your horn
needs 12 volts, and you've confirmed that. What you have left is confirming
how many amps your getting to the horn.  Your new or old horn may have it
stamped onto the casing. I'd guess 3 to 7 amps or so would do the job.

Possible causes of low amperage. A weak connection at the horn switch
caused by corrosion, pitting, or just a mechancal mis-alignment of a
doo-dad I'll call a "commuicator" This is a disk and wire gizmo beneath the
steering wheel which carry's the current from the fuse box to the horn
button, and then from the "pressed" horn button to the horn.  You might
locate said apparatus and then spray with your favorite contact cleaner and
see if that helps.

  Second, would be a possible inadvertant grounding of the HOT wire, which
is metaphorically speaking stealing your waterpressure, like when a toliet
flushes and your in the shower.

The ground fault could be confirmed by checking the ohm resistance of the
horn wire WITHOUT the fuse in.  This test must be done without any power,
speaking from experience and other boo boos, I've bought a new fuse or new
Volt ohmeter after such a mistake.

Anyway to find if the hot wire has some resistance: which it should not

Use the hot wire end that connects to the horn, disconnect it from the horn
for these test.
Put your ohmeter ground to the car body, and the other ohm lead connect to
the hot wire, there should be no resistance.

Now with the fuse still out push the horn button, there should still be no
resistance.  If your see resistance in any of the two tests, trace the
wire's route, begin at the switch if resistance is only when presssing the
horn button, otherwise either end is ok to start at. Look for frayed,
pinched, or abnormal wire connections, ie a big wad of electrical taped
wires with your tooting wire right in the middle.

Spark chasing takes patience, and is often a journey.


Mark Keller, *say , now that I think of it, my horn is really weak too!!!*
91 Carat WE
"Lazarus"

>My horn stopped working one

>I tested the two horn wires with a voltmeter and since pressing the horn
>button caused 12V to appear on one of the wires I replaced the horn with a
>new one for GB#5.88.
>
>However this did not do the trick. The button works fine. Both old and new
>horns work fine (when connected across the battery). Fuse number 12 blew
>during testing but I replaced it and the horn still did not work. The only
>way I can get the horn to work is by plugging the positive wire into one
>terminal on the horn unit and then grounding the other terminal onto the
>car.
>