[villagetinker]

OP, I tend to agree with the previous comment (smoked module), if your has self cancelling turn signals I have seen this exact same problem. It occurred when the owner was modifying the turn signal wiring and caused a short circuit. These modules tend to be expensive $150 or more, and the Yamaha modules can be difficult to find. You should be able to open the dash, and see turn signal module which usually plugs in. With the key OFF, unplug the module, then turn on the key and see if the light(s) are still on, if so then there is a problem in the wiring, if they are off, probably the module. If you have an older system, I have seen the internal contacts in the turn signal switch fail. Universal turn signal switches are available online however you need to see how many wires are on your existing switch, I have seen as few as 7 to as many as 9, they generally have the same color code.