Headlight Issue

1997 Lincoln Towncar. The headlights always worked perfectly until the low beam went out on the drivers side. Bought new bulbs and put them in. Then when I turn on the h/l's, they come on bright with the high beam light on the dash on, even when in low beam mode. When I turn on the high beams, the dash light stays on, but the headlights go dim (dimmer than low beams). Put the old bulbs back in and the headlights work exactly as they should (but without a low beam on the drivers side still, of course). Replaced the bad bulb only with a new one, and the headlights are still messed up but even a little weirder (it's like the lights are toggling back and forth between bright and dim, like school bus lights). Any ideas? The bulbs O'Reilly's sold me are 9007 and I had them triple check that that's the right ones.