1998 Peterbilt 379 turn signal issue. HELP!

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.
I have same problem as NIDiesel..one blinker works good..four ways work.. have you solved that mystery?
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.