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to answer your question on the ground: some of it is cost, some of it is convenience, and some of it is technical.  some items, like horns, draw a decent amount of current when used.  with thin gauge wire, like the gauge used on our bikes, a shorter ground means a cleaner and more consistent signal path for the device in question.  the principle holds mostly true for car stereos, but the same applies for any large current draw.

The horn is not really attached to the frame at all, is it?

There's like a clamp-type thing that wraps around one of the fork legs or something like that.  I think there's even some kind of rubber gasket type thingy between the fork and the bracket.  I doubt any part of the steering head / fork assembly has a good ground because it's only attached by bearings.  A frame ground has to be on the honest-to-goodness frame, I don't even think the swingarm is reliable (of course there's no electronics on the swingarm, I'm just giving an example).

Here's a simplified wiring diagram.   Hope it helps.

Can you explain your "downstream" comment?  I don't get it (nor do I really know which way the "stream" goes.  I mean I know electrons go from the - terminal of the battery to the + terminal, but I doubt that's what you mean.)  A switch in the circuit anywhere will work, but typically grounds are switched instead of +'s because they have the longest wire runs going all over the place.  If one of those wires breaks or shorts to the frame that's likely to do no harm (or sound the horn, which is good because it tells you almost exactly where the problem is).  That's better than blowing your fuse or melting your wiring harness.

Quote from: Wrecent_Wryder on August 10, 2006, 06:23:29 AM
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However, there are some aspects of DC circuits that puzzle me.

.................................. Why is it that some devices work fine with a frame ground, but most have their own negative wires, which seem to lead to.. a frame ground? 

With some circuits it makes sense to use the frame as the return connection. Take for example the high voltage spark circuit.  The plugs are grounded in the engine head and there's no place to connect a return wire for the negative connection at the plug.  Also the neutral switch is buired in the transmission so the same applies.  The engine case is connected to the battery neg terminal to complete the connection.

Most devices have a dedicated return connection because it's more reliable than connections to framework.

Quote from: Wrecent_Wryder on August 10, 2006, 06:23:29 AM
I'm guessing (mostly from the color-coding) that the horn switch is "downstream" of the horn itself, which seems odd, seems like there'd be more chance of the horn getting "stuck" as a failure mode, but it will of course work, and I guess it doesn't make much difference- a break in the circuit is going to be the same failure mode, and a grounded wire will too.

The location of the switch doesn't matter.  It can be located on the battery side or (down stream) on the ground side.

Quote from: Wrecent_Wryder on August 10, 2006, 06:23:29 AM
I "get" that I can just run a large wire (yes, with an in-line fuse holder) from the positive terminal on the battery to the relay and thence to the horn. I guess I could run two, one to the negative terminal as well. What's the downside of using a frame ground for the horn? Obviously, the designers thought there was some downside for the stock horn...

The downside is just reliability of the connections

Quote from: Wrecent_Wryder on August 10, 2006, 06:23:29 AM
In using a relay instead of running the increased current through the stock circuit, is the main concern overloading the switch (obvious), or the wiring as well? If the stock wiring will handle the 18 or so amps, and the switch is on the downside, what's to prevent one from using the "stock" positive wire for both the horn and relay (control side), the stock negative (through the horn switch) for the relay only, and frame ground for the horn negative, which would mean no new wires?

Nothing is preventing you from doing this.  Since the horn is only used intermittently there's not much chance of overheating and burning wires.  The reliability of frame connections  could be an issue.

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Quote from: Wrecent_Wryder on August 10, 2006, 11:03:58 AM


Thanks, I couldn't see any issue with doing it this way, but thought I might be missing something.

I might actually do this. It would be relatively simple to put the in-line fuse in the circuit, before the relay on the circuit but  physically right at the horn to protect the wiring from any possible damage, and I'm fairly certain of being able to get a reliable ground- the horn bracket is solidly bolted to the frame, and it's easy enough to test.  Seems a more elegant solution than running another wire all the way back to the battery when there's unswitched +12 right there anyway.

I like elegant solutions too.  Let us know how it works out.

Quote from: Wrecent_Wryder on August 10, 2006, 10:47:03 AM
The horn bracket is mounted to the frame, it doesn't move with the steering head (at least on mine).

Cool.  I couldn't remember.  I've never actually done any "horn maintenance."  Although, I would love to do an upgrade so something more respectable.

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I wouldn't call it "bone headed", but rather a good discussion on electrical understanding of the GS.

At least you discussed it and took feedback rather than coming to us and saying "I just installed LEDs in my turn signals and now they:

• Dont' work anymore
• All blink at the same time
• Blink very slow (or) very fast

A wise choice in my opinion.  It makes for easier tshooting later.

Wait a minute........................a GS's HORN draws EIGHTEEN AMPS of CURRENT!!??
Let me clean the feces out of my pants and the coffee off the monitor crt!!!!!!
Are you SURE about this? I am gonna be forced to bring home my Fluke and amp clamp next week.
That surely seems a lot for a two bit dime ass buzzer horn! I installed a throated horn on mine
and acquired a more "pleasant" "louder" "car type horn". Damn.

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