1998 Peterbilt 379 turn signal issue. HELP!

Thread starter #1
I have a 98 Peterbilt 379. Left turn signal doesn't work, right one works fine and the 4ways work. LED everything for lights. I've checked grounds and tried 2 different flashers and put in a new turn signal switch, have a wiring diagram, following the diagram and according to the diagram there is a left and right relay after the turn signal switch, maybe I'm an idiot but I cant seem to find them. Are there relays just for the turn signals? I have good 12 volts coming into the flasher, good flashing for right but when I back prob for the left it flashes weird but kind of works, but when it starts doing that I can turn the signals off and the flasher still clicks, but no lights flash.


Well-Known Member
Staff member
Depending on the truck, you can have seperate fuses and relays for each side, as well as separate circuits for the lights on the trailer.
Thread starter #4
Yeah, i figured it out, after trying the 2 flashers I had on hand, 1 LED and 1 regular flasher I ordered a new LED flasher and that cured my problems.