yeah, its definitely time consuming, but be patient and keep after it and you'll get it. Check your battery ground too. If its corroded, it could be draining your battery.
I'm with the others here. Check/clean every wire connection. It it probably grounded somewhere. A lot of the old bikes (hell, even some of the newer ones) had soldered wiring in the harness that over time corrodes or insulation that wears from vibrations and grounds out to the frame or other metal components. Trace every wire out and you will eventually find it. Good luck.