what caused my headlights to stop working?

The headlights have stopped working on my avalanche. First it was the high beam when the tilt wheel was moved from the upmost position, so I just drove with the low beams for a while. The highs would work when the steering wheel was all the way up so I know it's not the bulbs. Now the lows have stopped too. The auto sensor is working because the markers and dash lights come on properly. One mechanic suggested I replace the whole steering column. Seems a bit of overkill to me. Can you give an idea where to start? Oh btw, the system must be hot because the fog lights are working.