Most of the blinker issues I've found result in a fast-blink due to either a blown bulb or bad ground wire. I'm having the opposite problem - when I signal left, sometimes (not always) the signal sticks "on". I can see it lit on the instrument panel and also on the driver-side mirror. Resetting the stick and signaling again almost always works to get it blinking again. I've never noticed the problem signaling right (maybe just luck) or with the hazards, and I've not been able to reproduce it reliably. I thought perhaps some interplay between brakes and blinkers, but I can't recreate it with brake up or down - when it does happen, though, I'm usually slowing for a turn. All of the exterior lights are working properly when I've checked. I was tempted to just replace the blinker module but from the wiring diagrams it doesn't seem to "know" whether you're signaling left or right so I don't think it'd help.

Any ideas what I might try to trace this down and repair? It's a minor thing but damned annoying when trying to make a left and not get rear ended in the process!

 

So are you saying it is on the left only because this statement is confusing, "from the wiring diagrams it doesn't seem to "know" whether you're signaling left or right". I would replace the flasher relay. It's a WAG but that seems to be what your problem is pointing at.

Two choices: https://www.rockauto.com/en/moreinfo...24191&jsn=1761 or https://www.rockauto.com/en/moreinfo...24191&jsn=1764

 

Thanks PNW NBS Z71 - sorry if I was confusing. I've only noticed the problem when signaling left, but I can't guarantee it doesn't also stick on the right sometimes, I've just never seen it. Since the problem occurs only intermittently maybe I've just been lucky or forgetful. The second part about "doesn't seem to know ..." was from the wiring diagrams: if I'm reading them right the blinker unit itself doesn't have separate lines for left vs right, it just has one line for directional and a different line for hazards, so I wasn't sure if it was worth suspecting it or not. You're right, though - cheap enough and easy to reach, I'll replace that and if the problem doesn't go away I can try to chase it down further. Thanks for the links - I'll report back once I've got the new one installed.

 

If that relay does not fix then the WAG is the turn signal switch assembly. It is either this one : https://www.rockauto.com/en/moreinfo...24247&jsn=1708 or this one : https://www.rockauto.com/en/moreinfo...24247&jsn=1710.

You can see the difference in the switches at the end of the arm.

 

Access the turn signal switch connectors (there should be a couple) on one of the connectors terminal A should be light green and terminal C should be dark green. Turn signal on right you should have 12 volts at terminal A, turn signal left you should have 12 volts at terminal C. You should have no voltage at either terminal with the switch in the off state. If you have this you can safely say the multifunction switch is not your problem.

 

I pulled the dash open (had to replace the headlight switch anyway) and was able to identify the current blinker as part #15764135, GM has since replaced that with #10383321. Ordered one, dropped it in over a week ago, and so far I've had no further problems with the turn signals. Looks like the relay was the right WAG! Quick and easy fix, just two screws to remove the panel and access the blinker, the hardest part was wrestling the old one out by hand - there aren't any retaining clips, but it's in there at an angle and location that managed to defy every design of plier & grip I had handy, just had to be patient and bang up the hands a bit wriggling it out. Thanks all!