I once saw this hooked up backward. Nothing bad will happen, until, yes, until, you hook up a slave cable to the plug, and the other end is hooked to a 24 VDC power source. Oh yes! Sparks and smoke! The really funny thing about it, the contractor who were supposed to be fixing the truck, kept pulling out the plug, talking about it, and then plugging it back in. Destroyed the cable and plug.
Since they had replaced a starter, well, naturally, that had to be the problem. Then they stared to change the starter. I asked them if they wanted me to help troubleshoot it. "No, we don't need help from ITT.", The company I worked for. So I took a seat and waited for Light Show #2. And was NOT disappointed. Then they came looked at where the slave cables hooked into the battery box. Red on Red, Black on Black. Good to GO!! About then, the NCO who was supposed to keep an eye on things, came over and asked me to look at it. I went over, took a DMM and went from chassis ground to the middle pin. Nothing. Chassis ground to the outside part of the plug. 24 volts. I laughed until I almost expired. At some point in time someone had unhooked the wires at the plug, and reattached them wrong.
