How do I troubleshoot power to headlights, intermittent. bulbs & fuse are good. on 2002 Kia Optima

I have no power to regular headlight socket, I have good bulbs and fuse under hood. I have swapped the head light relay with fog light relay. Even disconnected battery to reset system. Problem just occurred, also air bag indicator came on at same time and continues. Both headlights are out, but not high beams (separate bulbs). What do I check next? Has this problem occurred to other owners? No service light is on.

Asked by for the 2002 Kia Optima
If you are SURE there are no blown fuses, the dimmer or multifunction switch is the most likely suspect. Just to be sure though recheck fuses!
Thank you for your answer. I found a wire crimped in steering column to the switch. It could have shorted out, replace wire, now headlights are on. Thanks again.
Should have blown a fuse though!