Peterbilt headlights stuck on high beam!!

Last night when it got dark, I turned my headlights on and now only have high beam for some reason. Truck is a 98 379. I had the same thing happen on my other Peterbilt and it turned out to be a bad fuse for the marker lights if I remember right. I checked all the fuses and swapped the relays around and didn't find anything. I even tried unhooking the trailer. Early yesterday I wound up pulling the end off my trailer cord when it got hung up while I was parking a different trailer. I dont think it is related but the problem did show up after that. I was going to try unplugging the trailer cord from the truck but forgot before I parked it today.
I have the dimmer switch on the turn signal control, I tried calling the dealer to find out where the actual relay is and they just want me to bring it in. I am heading back to Colorado tomorrow and want to try to check it out before I leave.
Any ideas???

 

Found the problem!!
Wire in the turn signal switch was broken inside the insulation.
A new switch was $75 from Peterbilt in Chicago so I just used about .05 worth of solder and fixed it.