success, and then some...... 8) I solved my voltage drop issue to the horns on my 82 1200 TS Mirage project build, with lots of help from all of you, thanks!
finished the re wiring, with relay, all new wires, inline fuse on the power source to the relay, power feed only switched off the relay direct to each horn, and each horn individually grounded full time. So , no power to the horns unless the ignition is turned on and the horn button is depressed, triggering the relay switch. Used all heavier wire than stock.
first test honk in the garage startled me, woke up the half deaf geriatric Golden Retriever sleeping at the other end of the house who jumped up startled and barking, and caused my spouse to come running out into the garage to see what the heck was going on. Bloody loud, using just stock horns it is WAY louder than a car horn.
Amazing what a full 12 volts + to the horns results in by way of sound volume. I am going to do the relay install in the same manner on the other two Laverda triples in the garage.
so, in the end, here is what I wound up doing.
I took the left handlebar switch cluster apart, took the dinky little horn button out, took a file to the end of it to clean it up, stuck a small file inside the turn signal housing where the horn button end makes contact, and cleaned that up nice and shiny.
then I traced the black/white ground wire out of the switch cluster to find, as Rene predicted, that the ground wire out of the switch cluster to its main white connector does not have a matching ground wire on the other side of the white connector. On Ren?'s advice, I fished the black/white wire out of the white pin connector, and made a direct ground wire connection to the bike's frame. Better, got a tiny little squeal/beep at the horns and 7.2 volts, but not nearly good enough.
then I went and bought a relay, wound up with a Bosch 5 pin relay (only need 4 pins) at the local Auto Value for the rip off price of nearly $17. Later I went to my electronics wholesaler where I usually buy my stuff, and bought 6 extra Tyco Electronics 5 pins relays, seemingly identical to the Bosch, for $3.85 each, bloody hell.
with my new found YouTube sourced knowledge that pins 85 and 86 are the control switch side, I traced where the Laverda main wiring harness has the two wires out to the sub loom to the horns, unplugged the small horn loom and removed and discarded the stock four wire horn sub loom, not to be re used. The stock horn sub loom has two power wires (one for each horn) and two ground wires (one for each horn), and the stock wiring has power full time to the horns when the ignition is switched on. The horn honking with the stock wiring happens when the horn button is pressed, going to ground through a tiny little pin and tiny little spring, completing the circuit. Anyway, I figured out which of the main wiring loom output wires to the horn was power and which was ground, which turned out not to matter to wiring the relay anyway. I then made new wires to connect the two horn button outputs from the main wiring loom (just plugging onto the stock connectors,) and used the new wires to connect to each of pin 85 and pin 86 on the relay. I mounted the relay under the seat on the rear fender simply because that allowed me to use just a short large power feed to the relay from the battery as well as use an existing hole in the fender for mounting. I did not want to drill any new holes, otherwise I could have put the relay just about anywhere I could have hidden it. To test proof of concept, I turned the ignition on and pushed the horn button, the relay worked and I could hear the little contact switch inside the relay click.
from there it was just a function of running a heavy power feed cable (with inline fuse) from the battery positive terminal to terminal 30 (power in) of the relay, then running a single power feed wire forward from pin 87 on the relay to the same location on the wiring loom just above the carbs where the control wires for the horn are also located, just to make everything neat and logical. For my wiring circuit pin 87a is not used on this 5 pin relay and is not needed, if I could have found a four pin relay to buy I would have.
then I made a brand new sub loom for the horns, (power wires only, no ground wires) tied two heavy duty power wires together into one connector to plug into my power feed wire above the carbs from the relay, and ran one heavy gage power wire to each horn. Then all I needed was a ground for each horn, so I made short ground wires, plugged into the horn terminal with a short run directly to the bike frame. All looks very neat and tidy, I used professional connectors, every connection is shrink wrapped, etc. The horn power is ignition switched, as the horn button wiring that triggers the relay does not work unless the ignition is on.
a lot of time for me and my electrickery challenged brain, and a couple of hours fabrication believe it or not, the guys that are good at this stuff are welcome to laugh at me, but I did eventually get a great result. Oh, and for the commenter that warned me about the brake light circuit, I did check and the brake light works fine, thanks for the warning! My hat is again off to you folks that do this stuff for a living, for the less experienced of us there is always something to learn, now I clearly understand how a relay works and how to wire a relay for various purposes. The relay control side, pins 85 and 86, don't care if they are controlled/switched by power or ground, and there are at least a couple of other ways to wire the horn circuit I described, in my electrickery ignorance I just did not like the idea of having full time power running into the horns (with the ignition on) as the stock wiring does, so at the horns I used constant ground and switched power.
I am also thinking this voltage drop issue caused by the horn button, grounding issues, and deteriorating wiring and grounds, must affect a lot of the existing Laverda triples, I wonder how many horns out there actually work properly or at all......?? I got driven into addressing this issue because my bike has to pass a mechanical safety inspection so I can register it, I don't think I would have spent the time and energy otherwise on this issue, frankly.
thanks for all the help, everyone, sincerely appreciated!
Paul LeClair
ps the inline fuse receptacle does have a sealing top cap and will be water tight once I go out and buy the correct sized fuse, the fuse I am using at the moment is too large to allow the top cap to snap into place - one more run to the Auto Parts store required....... :
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