There are 4 wires on the back of the alternator.
The Dark blue/red (large one) one should have 12v at all times. It has a fusible link which may be blown if no power there.
Red: This one should have power when the engine is running. Again, there is a fusible link on this wire.
Black should be grounded at all times.
LT Green Connects to the voltage regulator I believe is another ground.
Both fusible links are located on the Back side of the left wheel well. The first is black, Gauge unknown, The second is an orange 20 Gauge.