Sorry about taking so long to post about my installation of a turn signal buzzer but I forgot about how involved a project it was until I tried to write about it. Instead of just showing what I did I also answered questions that I thought someone might have who wants to install a buzzer themselves.
For a professional electrician by just taking off the seat you can cut the large wire loom (attached at some places to the left tubular frame by wire ties) length wise to tap the relevant wires and because the wires aren't color coded you'll need a digital DC mini clamp meter to identify them.
For every one else including myself you'll have to take off allot of parts to get access to where the wires connect to the rear turn signal lights.
The finished installation
The Piezo Buzzer I use ( HJ-650, specifications are; 95 DB, 4-28 volts @ 15 MA, 43 MM diameter, waterproof ) isn't commonly sold any longer as far as I can find out but I assume there are similar ones available. I'd get a large one because a 30 MM diameter piezo with about the same specs isn't nearly as loud as the 43 MM above one ( when both are using 2 volts ).
Why do you need a buzzer this loud ? the answer is to compensate for the LED lights that only use 2 volts. This buzzer puts out an acceptable volume at 2 volts but is designed to be much louder at 4 - 28 volts.
Only use piezo buzzers and piezo buzzers that have a driver or built-in oscillator circuitry which without it is totally useless and could also damage the scooter. As a precaution test it first by connecting it up to a 12 volt battery using a 1 amp in line fuse in the circuit to verify it works.
Getting to the wiring -see pictures 1-3; use picture 1 for reference
To begin first remove the seat #1 and in order to remove it open the trunk then take out the two bolts in back of the front seat and slide it forward.
To remove the seat rack #3 you first have to remove the small panel #2 that's on the top back of the rack by removing the two screws underneath it.
Take off the rear seat #4 there are two washers 1.5 MM thick that are used as spacers (see picture 2) when I took my seat off one came off, if this happens to you you'll have to glue it back in place, the product Goop works well.
A tricky part is removing the chrome plastic parts #5 (also see picture 3) that fits on around the rear turn signal lights. After you take out the two screws then the only thing holding it in place is ( B ) that goes into a push-on type fastener. Referring to picture 3 gently slide #5 out in the direction of the arrow by pushing on it from position ( A ). Note because #5 is flush to surface at position ( A ) you'll first have to move it out just enough to be able to push on it.
Two hidden screws (total of 4 for both sides). you can see #6 from below and #7 is deeply inset.
You don't need to completely remove the side panels.
Wiring -see pictures schematic, buzzer wiring, left turn and right turn;
Always have the ignition off when wiring !!! Who knows if you miss wire something or short out a wire it might damage the main board.
Initially when you first tap into the turn signal wires verify it has the same electrical polarity as my scooter as shown in the schematic picture. Because the voltage is pulsating a dial multimeter set in the 5 volt range works well.
If possible don't cut the Vectrix wiring your taping into.
Use a grounded type soldering iron.
I soldered all electrical connections except the ring terminals connections to the buzzer, ran most wire in 1/4" split loom tubing, used 22 gauge stranded wire, used wire ties and electrical tape where necessary and used heat shrink tubing for the diodes.
One thing I found out is the turn signal switch on the handle bar uses a low power level current so you wont be able to directly operate a piezo buzzer using wiring from there.