On my 97 Cadillac Deville, i installed a new headlight lens with the housing on the passenger side. When i did the installation, i had to unplug the wiring harness, then i plugged it back in. Now, my driver side headlight does not work, none of the lights connected to the wiring harness work. But when I turn on the high beams all the lights mysteriously work, but when i turn my lo beams back on, no lights work. any ideas?

 

Look for a connector pin that may have got pushed out of the harness when you plugged it back in, or a broken wire from handling the harness. It sounds like most of the lights aren't getting power, and when you turn the high beams on power may be going back through the bulbs and powering everything else. There are other things it could be too, but having crimp pins push out isn't uncommon.