No gauges... or fan

Well I just wrapped up my final semester of school, and what happens to me on the last couple of days??? Electrical problems... Heres what happened, and what continues to happen.

My 74 260Z, All of a sudden, has lost all tach, fuel gauge , oil gauge and fan function. And my amp gauge reads a varying drain, even when the car is revved. Upon a glancing observation I found that all the gauges use the same green-white wire. Continuity was... continuitous( is that a word?) through out the harness, however after the plug box I lose track of the wire... My question(s) 1) WHats going on here?!?. 2) Where is the beginning of this green/white wire. 3)am i on the right track??

Oh yes... one more thing... The black/ground wire is also shared, it also showed continuity through out the harness... but I see no undone grounds.

Thanks!!!

-Patrick