Hardwire satellite receiver XACT XTR7

Hi, I posted a topic a while back about hardwiring an XACT XTR7 receiver. The cigarette adapter had no circuit board, so I followed the instructions of the person that responded and just cut the wires and used the tip one as positive and the one on the sides as negative. It worked fine, but I quit using the radio in that car and took it out and was going to install it another car. I ended up taking it out and not installing it for a month, and I did not mark which was positive and which was negative. Will it be okay to just touch them to a batter to see which is positive and which is negative? If i do them in reverse, will it hurt anything?

if you've got a multi meter with a continuity tester on it, touch one lead to the outside of the plug going into the unit, touch the other to each of the wires, the one that connects to the outside of the plug is your negative.Life moves pretty fast; if you don't stop and look around once in a while; you could miss it.