I've had an issue with the driver side blinker since I bought the truck last year that despite trying everything I could find on MUD, I couldn't figure out. Essentially the blinker would flash once then lock up and stay steady on, but it would only happen when the headlights were on. No headlights on, it worked perfectly. I've tried running new grounds, new bulbs, cleaning the contacts, checked the flasher, and even went to the old school 1034 bulbs instead of the 1157 because I read the voltage is a little different and the flasher can be sensitive to that. Nothing worked. I have always noticed that the driver side running light on the blinker was a little brighter than the other side and today I realized why. The small (shorter) fillament was lighting up when the headlight/running lights went on on the driver side but it was the opposite on the other side. I pulled the bulb and but it part way in backwards and it obviously flipped. Held it that way and ran the blinker and what do you know! Problem solved! It looks like somebody rewired the housing at some point and flipped the wires. Simple but FRUSTRATING problem that I couldn't figure. Anyway, hope this helps someone because there are loads of blinker threads but nothing with this exact situation. Hope this helps some other poor sucker down the line!