Well, it appears that Howie has been right all along;
the rear end is the place to go.
I had to pull the side panels off anyway to get off the rear cover, so I went ahead and pulled out the tool tray so I could chase the yellow wire from the rear brake pedal switch. It crosses over to the left side and then gets buried in the wire bundle headed to the rear before getting joined with the front brake switch. The junction must be somewhere inside the left side wire bundle. Not worth finding exactly where, IMO.
After you get the rear covers all off (have to remove the luggage rack first), the tail light assembly wiring all goes through a single quick-disconnect connector on the rear, left hand side. The entire tail lamp assembly can be unplugged and removed with one bolt so that you can work on a bench (that's handy!). There is only one yellow wire going through that connector, then in the first 3-4" is the split for the two bulbs. It is hidden in a short piece of tubing used as a loom, but the tubing is only taped into place, and you can slide it up the harness to gain access to the splices. The splice is only taped-up under the tubing as well. This seems like a good place make the connections.
First, I cut out the brass butt splice in the picture above. Then I took the two wires running off to the tail lamps and spliced an 8" yellow extension wire to them so I could make my connections more accessible under the seat after re-install. To the shorter wire going back to the connector I also added an 8" extension, but this one is yellow with a brown tracer so that I could keep track of which side is the supply vs the load. I then unwrapped the ground junction in that same wire bundle and soldered an 8" black extension wire to it. All new splices were covered in shrink tubing. I pulled all three new wires up through the same piece of loom tubing and then slid the tubing back down over the splices
On the new yellow wire I crimped and soldered a male molex pin. The yellow / brown wire (supply side) gets a female molex pin. I covered the two molex pins entirely with shrink tubing except for the contact portion of the male pin (just the last cm or so). The module wires were already prepared the same way (but in reverse). The module's red wire gets the male molex pin as it connects to the supply side. The module's yellow wire gets the female as it will hook up to the new yellow wire that runs to the tail lights. I color coded the shrink tubing to help identify which wires go together when installed. Yes, I am anal retentive...
With the connectors arranged this way it will prevent accidentally connecting the module in reverse polarity, and if the flasher module happens to crap out I can just disconnect the two molex connections and reconnect the yellow and yellow/brown wires together on the bike side and it is back to stock. The ground wire (black) I just used a standard spade lugs (male and female) to make the connection from the extension wire to the module black wire.
Here's a picture of the module fully wired to the tail lamp assembly, and then a closer look at the wiring connections. Note the module yellow wire is disconnected to show how the molex pins are prepared. After connecting the molex pins I gave them each a wrap of electrical tape to help keep out moisture and keep them from sliding apart, though the friction is probably good enough.
After reinstalling the tail lamp assembly the module and mode switch were pulled out and under the rear seat area for easy access.
Now to the important part: How does it work?
Well it works pretty much exactly as advertised. There are a whole bunch of modes with different flash rates and delays that can be selected using the switch. What I found is that all but the slowest flash rate is unusable when using incandescent bulbs in the tail light. Anything faster and the latency of the incandescent bulbs means that the bulb will not reach full brightness before the flasher turns the bulb off again. This means that during the flashing interval the brake light will never reach full brightness. Obviously, that will have exactly the opposite to the intended effect of getting drivers attention.
At the slowest flash rate the bulbs seem to reach full intensity and the flashing should be somewhat attention getting. The below video is the slowest flashing, 5 flashes before steady mode, with no delay enabled. In the video it appears that the flashes are not equal in length or brightness. That is just an artifact of the video compression. The flashes are equal and all reach the same intensity.
Click for Video
But, the effect is not quite as eye catching and attention getting as what I was hoping for. It is only the equivalent of flashing the lights by cycling the brake lever. So, now it's on to phase II, 1157 equivalent LED upgrade for the brake lamps. The quicker turn-on time of LEDs should allow me to run a faster strobe rate, which should give the affect I'm looking for.
[note] Since I have used this thread for documenting my install, I have also edited the thread title to reflect it.
