The regulator is labeled A, S, I from [passenger side to driver's side (IIRC)].
A = battery voltage. White/yellow IIRC.
I = ignition. Lt Grn/red.
The regulator's letters (ASI) are embossed into the back of the regulator. Then just test the wire in question to see if it's hot with the key off (A) or only with the key on, car off (I).
Good luck.