Left turn signal issues
Left turn signal issues Recently went to get a state inspection and failed because my left turn signal wasn't working, I had no idea because I'm running an electronic flasher and led bulbs up front and of course the electronic flashers just continue to blink like normal if you have a bulb or something blown out. Initially checked the bulb by moving it to the other side and the bulb functioned fine so I figured it had to be the socket since it looked pretty bad. Swapped in a new socket and still the left signal wouldn't work so I broke out the multimeter and started taking measurements. I am getting continuity between the pins in the socket from ground to the pin for the brown wire (power for one filament) but have no continuity from ground to the pin for the light blue wire (power for the turn signal). I also tested voltage with the other side and with the turn signal on for that side or the hazards on I was getting voltage but on the driver side I have nothing. I also measured resistance between the 3 wires on the driver side without a socket attached and once again I get continuity between ground and the brown wire but no continuity between ground and the light blue wire. I know the signal also goes through the drl module so I plan on testing the connections there my question is can i just connect the two wires together if I find out the drl module is the problem? I already bypassed the drl's years ago by doing the drl bypass on the drl module so drls aren't a concern for me.
So wanted to give an update, I went ahead and removed the drl module and using my multimeter discovered that I was getting power going into the drl module. I went ahead and ran a jumper from the wire coming into the drl module to the outgoing wire for the turn signal and then the turn signal worked when I turned the hazards on, I also had continuity at the socket. Went ahead and spliced the wires together to bypass the drl and now it works as it should.
Joined: Nov 2003
Posts: 11,328
Likes: 346
From: Jacksonville, FL (originally from Toronto Canada)
Good job of diagnostics! It's really nice to see step-by-step testing rather than just throwing parts at a problem.
Since the DRLs and turn signals share the bright filament of the front bulbs, the DRL module has a pair of relays to switch one side or the other between steady and flashing power depending on turn signal use. It is somewhat unusual, but either or both of those internal relays can get stuck - usually in the default DRL mode as yours apparently did. This is why I always recommend splicing the light blue and dark blue wires with their white stripe counterparts to bypass the DRLs rather than the internal solder solution that some recommend. The external mod makes it obvious that it has been done, simplifies return to stock should it ever be needed, and eliminates any possibility of those internal relays causing a problem in the future.
Since the DRLs and turn signals share the bright filament of the front bulbs, the DRL module has a pair of relays to switch one side or the other between steady and flashing power depending on turn signal use. It is somewhat unusual, but either or both of those internal relays can get stuck - usually in the default DRL mode as yours apparently did. This is why I always recommend splicing the light blue and dark blue wires with their white stripe counterparts to bypass the DRLs rather than the internal solder solution that some recommend. The external mod makes it obvious that it has been done, simplifies return to stock should it ever be needed, and eliminates any possibility of those internal relays causing a problem in the future.
