normally they wont have signal wires. but if you are needing to determine if one is power and one is ground you can use a power probe or test light to determine which is which. on new cars you could use bi directional controls to activate the fan and see which is which. But i am assuming this is for a Skyline so you can power up the fan manually and see which what the fans spin. since they are polarity sensitive you can determine which is power and which is ground by the direction it turns.