But because I didn't find a good place to mount a terminal strip, I instead followed the wiring schematic included in the article posted the technical library here: https://modernvespa.com/forum/topic449.
I don't have a lot to add to what can be learned in those two posts. What I thought I would do is provide some S150 specific photos of where I found good connections and a few details about my own installation.
My basic parts were these:
Radio Shack Piezo Buzzer, part #273-060 ($4.49)
Radio Shack 1N4005 Diodes, part # 276-1104 ($0.99 for two)
18 gauge wire (red, yellow, and green) (Note: wire colors were based on what I had on hand)
butt connectors (both 18-22 gauge and 14-16 gauge)
After exploring possible areas to connect everything, I found the best place to be in the handlebar cover area. I removed the cover by following the instructions in the user manual (described for the topping up the braking system fluid). In my case, removing that involved also removing my flyscreen, which was preinstalled by the dealer. The downside was it took a bit more time and I was unsure how much of the flyscreen I had to remove. The upside was that I learned everything I'll ever need to know about totally removing and reinstalling the flyscreen, as well as the best way to adjust the exact position of the screen.
The handlebar cover is like a clamshell, and splits apart right at the seam that runs along the top dead center of the cover. It took some wiggling and just an ounce or two of force to get the two halves to let go and split apart. Once they were apart, I found a few different options for splicing into the left and right blinker wires. I was hoping to avoid splices and to find some kind of unused connector that runs to the blinkers (perhaps for the optional alarm system). At first, I couldn't spot anything of the kind. But I finally did. It is a two-wire connector, and runs to the right and left blinkers only -- nothing else. It was wrapped around some of the internal frame structure in a way that it was hiding down below that structure and to the rear of the handlebar area. Below, I have pics that show the connector (one a close up).
I tested the connector with a multimeter to make sure it would do what I wanted. Then I located a spot for the buzzer. I basically used two plastic zip ties to attach it to a thick cable housing that ran across the front of the handle bar area and below the instrument cluster (pictured below). Then I followed the wiring diagram in the post from the technical forum. It worked without a hitch.
I'm attaching the pics below with short descriptions of how and where I connected everything. I ended up using some 18 gauge bare solid copper wire, butt connected to the coated wiring, to make little "mini plugs" or prongs that slip right into openings on the previously unused connector. The copper prongs slide in with just enough resistance to be a nice snug fit. And they disconnect with about the right amount of resistance as well. The entire install is non-invasive and can be removed without a trace.
Here are the pictures and some short narratives. Hope this is of help to anyone thinking of making this modification (which I am really glad I made), especially if he/she is doing the mod on a Vespa S. Feel free to pm me if I haven't been clear enough or if you just have some questions that I might be able to answer.
Here's the basic lay of the land when you get the handlebar cover off. The unused connector is hard to spot (blue circle). I have a close up in the next photo, but this photo gives an idea of where to find it.
Here's a close up of the unused connection I located. It's out of focus, but you'll get the idea. I pushed it back up behind the black cross-member it wrapped under, and brought the wire back through and over the top so that I had more options on where
Using zip ties, I attached the piezo buzzer to a cable housing that ran right through the middle of the handle bar area, just underneath the instrument cluster. I cleaned the ties up by clipping off the excess (after this photo was taken).
I joined 18 gauge wire to the ultra thin wires from the buzzer by using a butt connector. I didn't have butt connectors small enough for the wires on the buzzer, so I used a one sided butt connection by using a 14-16 gauge connector to join the the 18 ga
I couldn't find a ground connection I liked in the handlebar area. So I ran the yellow ground wire (I'm a former boat owner -- it's hard not to use yellow as my ground color) down to this bolt above the horn, behind the front panel.
I made these so that each wire coming off of the diodes on the hot side of the buzzer could "plug" into the connector. The bare solid copper wire prongs worked perfectly for that purpose.
Here's the entire set of connections. Using a 14-16 gauge butt connector, I crimped both diodes onto the 18 gauge wire coming from hot side of the buzzer. Then each "plug" wire for the connector was crimped onto an individual diode. I later w
It's all bundled (and taped) together. I later wrapped electricians tape around the "plugs" going into the connector (green circle), but I wanted you to see how it looked. And then I zip tied the whole thing under the buzzer.
