I'm replacing a light fixture in the garage (one of two). I stupidly lost track of how it was wired originally. I have two black wires and two white from the ceiling box (house built in 1970). When I hook up both black wires to the black wire from the fixture and the whites to the white, only the other light garage fixture turns on. When I hook up one of the black wires to the black wire from the fixture and one of the whites to the white wire from the fixture (capping the others), only the new fixture turns on. I'm pretty sure there were only two wire nuts originally. I know there is a switch loop but the usual procedures aren't working (hook up hot to white switch, connecting the remaining like colors,etc.) Any help would be appreciated.