Marinco Mod Help

[Stroking]

So i went to do the marinco and the previous owner only had an aftermarket two prong connector on then end of the heater plug. When connecting it up i put the green wire where the green hold is but the two other wires are both black. I wasnt sure so i just put one in one hole and the other one in the other hole. I went and plugged it in and it didnt work. Before i pull the plug again does it matter which side goes to which?