Sorry, I'm not thinking straight. The first thing the supply does, is go to the turn signal switch. When you turn the switch to the left, or right turn position, then you get power to the flasher, when the key is in the run position. So to test this, turn the key on, then put the turn signal on in ether left or right turn, and there should be power @ the flasher. Again I apologize, for the mistake. If there is no power @ the flasher, then you will need to trace the wires back from the switch to the flasher. This may also help you. Look at what color the wire is @ the turn signal fuse, on each side of the fuse, if you can see it. Trace this back into the cab. This will be your supply for the turn signal switch. You will need to unwrap the wire harness to trace these wires. Once you find and fix the issue, you will need to tape your wires back up with electrical tape.