The right rear turn signal failed. It wasn't the bulb. I thought it might be the turn signal relay, which was stupid since there's only one lead coming off the relay that governs both lights and the front right light was working.
I then figured it would be some corrosion fault at some junction and spent a few hours trying to find in the wiring harness where the single lead out of the turn signal relay diverges into the lines that go to the front and rear of the bike.
No joy. It's a jumbled mess of wrapped wire bundles.
Of course, I violated my first rule of diagnosis: start with the most recent change.
Trying to verify that it was a junction problem my thought was to see if I had connectivity from the turn signal relay assembly to some easily accessible point along the wire running to the rear.
I opened up the tubing which housed the wire bundle for the rear turn signals and brake light. The blue black line was the one powering the right rear light. To my shock, it was loose.
When the Ohlin's was installed I'm guessing they pinched the wire bundle crushing the bliue/black line. It took a while to separate completely.
I've spliced it back together and the turn signal works. Now it's just a matter of bolting everything back together again and hoping I didn't introduce any new faults as a result.
