i found that by placing the car in reverse ( not while running preferred) then with someone watching from behind, tighten the adjusting screws when the back-up lights come on.
but the most frustrating thing that happened to me... i installed two of these from N.P.D. and both failed within a week. so i just reinstalled my original, and said "they can hear me back up, i don't need them stupid lights anyway"
but if somone knows a good replacement, i may reconsider.