Why would both turn signals blink?

[DirtDonk]

Better late than never! Way to keep at it.
Glad you found the problem.
There’s no way it could’ve ever been the flasher units I don’t think, because they’re just not wired that way.
Could have been a turn signal switch, I suppose, but not a very common failure. Not sure I’ve ever heard of one failing in such a way that both lamps light up.
But the hazard switch seems to be a common theme here, what with all the interrelated connections with the turn signals.

And the falling apart in your hand? I guess that was a dead giveaway right there!
Too bad it didn’t fall out from under the dash six months ago, and announce its presence before all the head scratching and neck twisting work!

 

[nvrstuk]

Proof right here you can be low on blinker fluid!!! Look close...

 

[abn373]

Better late than never! Way to keep at it.
Glad you found the problem.
There’s no way it could’ve ever been the flasher units I don’t think, because they’re just not wired that way.
Could have been a turn signal switch, I suppose, but not a very common failure. Not sure I’ve ever heard of one failing in such a way that both lamps light up.
But the hazard switch seems to be a common theme here, what with all the interrelated connections with the turn signals.

And the falling apart in your hand? I guess that was a dead giveaway right there!
Too bad it didn’t fall out from under the dash six months ago, and announce its presence before all the head scratching and neck twisting work!

Yeah, that's why this forum will always be better than the Facebook bullshit. I have been busy for months with other stuff and messing with it here and there when I had a chance, pouring over wiring diagrams, etc. I knew I had it all wired correct (well the flasher modules were inverted, but I fixed that) then I saw this post . I am not the OP, and went out and pulled the dash hazard switch out...and magic mother f..... I went in the house and showed the wife the hazard switch..."Look at this 50 year old piece of shit keeping the Bronco off the road" and then I realized that could be reflected back at me in the mirror

 

[nvrstuk]

Glad you persisted and figured it out!

 

[abn373]

Well I got my new dash hazard switch and just installed it. All the lights and blinkers work perfectly now. $19 part kept my Bronco off the road for all this time.

 

[abn373]

Well I got my new dash hazard switch and just installed it. All the lights and blinkers work perfectly now. $19 part kept my Bronco off the road for all this time.

Dammit! after I actually put the hazard switch back into the dash it went back to doing the same nonsense again. everything worked 100% when the switched was wired and just hanging under the dash. So I just pulled the connector out of the back of the switch while the switch is still in the dash and the turn signals went back to working again.

 

[Brush Hog]

Bad ground. Dash probably isn’t grounded properly. That will cause all sorts of gremlins. Make sure it’s bare metal to bare metal paint, powder coat and rust will cause problems. Had same issue when I did painless harness. Had to sand spot on back of dash and ground it to the body below windshield. I have found that new parts/switches are more likely to be bad out of the box than the 50 year old ones I am trying to replace.

 

[abn373]

Dammit! after I actually put the hazard switch back into the dash it went back to doing the same nonsense again. everything worked 100% when the switched was wired and just hanging under the dash. So I just pulled the connector out of the back of the switch while the switch is still in the dash and the turn signals went back to working again.

Solved it! Ok fellas, you are never going to believe this was the cause of the problem the whole time. So everything worked when hazard switch was hanging down, I put it in dash and back to issues, I unplugged harness and turn signals worked again. I used multimeter on the harness, and it seemed like it was fine. I dismounted switch and plugged switch into harness while hanging and everything worked. So, I thought some weird grounding issue when switch touched metal dash, which made no sense, but I held it against dash and everything worked. So dumb test, but I left the key on and turn signal on as I installed the hazard switch back into the dash to see when it would stop working properly. I was fine the whole time...WTH?? So I put the knob back on and ran the tests...AND all the issues came back. Took the knob off and all fine. I have aftermarket billet knobs. Guess what? the knob tolerance allowed the knob to sit on the shaft where when pushed in, it would turn off hazards, but apparently the shaft was just the tiniest bit pulled out and when the turnsignals energized and went through the hazard switch it was have just enough of a connection to cause the fault. I backed the knob out the tiniest bit and retightened it and all issues are corrected. CRAZY that this was the issue the whole damn time!