Did some more troubleshooting today, and from what I can tell the problem may not be any of the sensors listed above. The battery voltage is fluctuating wildly. When it's running good, the voltage is rougly 10-11V, When it starts to fall on it's face, the voltage drops down to 7-8V. I've seen it go as low as 4V. But then once the car dies, it goes right back up to 12V.
Anyone have any wiring digrams for the Charging circuitry?