I had a similar thing happen driving back to OKC from Kansas City, an Oklahoma county sheriff around Perry pulled me over for no taillights but my brake lights worked. I had figured out they weren't working when I stopped for gas on the way back, he was pretty nice about it. The switch failed sometime on the trip, that headlight switch was a pretty expensive piece on a RX-7, I ended up finding a schematic and soldering a jumper wire where the solder connection on the circuit board broke. Much cheaper than an $800 replacement part.