The problem you are describing, sound like a ground problem. I don't have a wiring diagram for a 2000 XL. Always start with the simple. Make sure the ground connections are clean and tight. There are 3 of them; the battery, the frame, and next to the starter.On newer model XL's the signals have 2 wires, purple=power, black=ground. Make sure the ground wire has not been damaged. If the lights do not have a ground wire, make sure the metal they are attached to is clean and not painted(paint will not conduct electricity). Check were the turn signals connect to the harness. Make sure the plug and sockets are clean and free of corrosion (green or white color). If your bike is equipped with a mechanical signal flasher, it may need replacing. I hope this helps.
2006 XL1200c. Stage 1, Chain drive(say no to rubber bands). I am a Rider, not just an owner.