Hey,
I recently pulled apart the dashboard in my car to get at the heater core. So, naturally i had to unplug the battery to work safely. Well, I was an idiot and unplugged the positive terminal first. Realized my mistake soon after and unplugged negative/put back positive. I finished putting it all back together yesterday and when i went to plug the negative back in, sparks flew and i think the headlight motors went apeshit.
Now, this is where my issue lies. I put the ground onto the positive because i was fairly sure that's where it used to be, but when i used to work on the truck, the ground was at the negative terminal. is this why it's sparking?

long story short: positive has ground, negative is unplugged. plugging back in headlights go crazy and sparks fly. please help.

 

The car is negative-grounded.

 

and it doesn't matter which cable you remove