I can't get the high beams to work on my 2000 Silverado truck. I was using them in the mountains and they just stopped working. Both highbeam lights on each side will not come on. What can I check to get the highbeams to work again. My mechanic worked for 4 hours and could not fix the issue. I really need your help with this problem. It is not the switch on the steering column.Thanks in advance.