It won't be the flasher relay, sounds like the Bulb, wiring or the bulb holder. Have you swapped the bulb with another known to be working one?

 

Yes, I have aftermarket blinkers (not LED) mounted to the shock mounts. I switched the blinker plugs from left to right and the problem is reversed... the left blinker does not work now. So all wiring and bulbs are good, at least from the plug under the seat. The lighting is British Customs plug and play.

These are my turn signals:
http://www.british-customs.com/mode...oms.com/modernclassics/triumph-scrambler-efi-2009-2016/bullet-turn-signals-html

This is my tail light.
http://www.british-customs.com/modernclassics/triumph-scrambler-efi-2009-2016/retro-taillight-black

 

OK, I just plugged in the old stock tail light assembly (which I can't believe I saved) and same problem. Right rear blinker does not work. I can hear the flasher working. And again, all three other blinkers work. The problem must be north of the under-the-seat wiring loom plug.

Are the front and rear blinkers on two separate circuits, or are they linked together somehow?

 

If you did need to buy a new relay don't even think about getting it from Triumph. It's a common one used on small European cars, just search google, or ebay with the part number, 4db003750-70, you can get them for a quarter of the price Triumph quote you.

 

You need to do some testing to pin down the fault. Get a 12v test lamp ($10 from any automotive store) and/or a Multimeter ($25-$100). and start checking the pins at the flasher connection to the bulb socket. I suspect you have a bad/broken wire between those two ends. The front/rear lamps on the same side are wired to the same circuit from the relay....so if only the rear is failing, then it's likely not the relay itself.

You should pick up the Haynes manual for your year bike...it has the schematic wiring diagrams for all circuits to help you troubleshoot. Spending the money on the manual is a great investment that will pay for itself the very first time you use it over taking the bike to a pro mechanic.

 

Thanks guys, that wiring diagram looks like spaghetti to me but thankfully I found the checking procedures. Still, strange that only one signal doesn't work since the left and right sides are two separate circuits. Will give it a try tonight.