Check out this example of AG-leaders manual:
You can see the wire colors of the WAS plug,
I guess
red … 5 Power supply (5V or if radiometric type VBatt)
green… Signal
black … GND
But keep in mind, if the senor is not an radiometric type and You connect 12V to 5V you WAS is death!!!
Edit:
same Manual:
but look red / black wires a crossed 
It seems outer wires are sensor voltage supply, inner is signal
