98 suburban k1500 Lt

I have been chasing an electrical issue for a while now. #15? fuse for the dtr and fog relays keeps poping. when the fuse is blown i have no running lights, or dash lights. ive searched the forum and tried what others have found to be the problem, tail light circuit boards, headlight/dimmer switch. ive looked over wires and have had no luck finding my problem. tonight i noticed when i put a fuse in, i get nothing, before the lights would work for 5 mins or so then pop, now no lights at all. i checked with a meter at that fuse terminal and there is no power. where do i go from here? dtr relay? if so where is it located? the fuse is labeled dtr and fog but i dont have fog lights.
any help would be greatly appreciated

 

If you can unhook one of the running lights, do so. Replace fuse, go from thiere. If the fuse blows, rehook, then unhook the other. You'll have to isolate the fault.