Slick 60's

Ive got a problem somewhere.

When I put on the turn signals (L or R) both rears flash in addition to the proper front signal.

When I apply the brakes, everything quits flashing and stays on.

Where should I look first?

As to both rears flashing, I would say you need to start looking at your turn signal switch.
The brake light overrides the emergency flashers, though. I never have liked that.

The switch does not self cancel, maybe a short in there somewhere.

Self canceling is mechanical, not electrical. I'd start with wiring and always look at grounding first. Improper grounding can do some funky things. I've been fighting this on mine recently. In the end, I had a bulb that was all honked up. But grounds were also an issue.

Hmmmn, I guess I will pull all the bulbs and check the sockets. I found a trailer harness tucked up under the bed that looks like it was spliced in with tape, there is a good possibility that the problem is somewhere in the mess of black tape.

I hope its not raining tomorrow.

I think you have a short between the left and right turn signals

do you have a multimeter?

BJCGC
I just think you have some wires attached incorrectly.
I'm not sure if I can make this clear with just words, but I'll try. And note that I'm only talking about the turn signals and brake lights here.
In the turn signal cam under the steering wheel, there are 7 wires attached to the mechanism. One wire each for every turn signal lamp. One on each corner of the truck. They generally are wires with a stripe.
When you move the turn signal to "right" turn, the contact inside makes a connection with the two wires for the right front and rear turn signal bulbs. Note again that I said front and rear all have separate wires.
There is one wire that grounds to the horn rim and it will be a solid color.
Then, there are two solid color wires that go to the center tap of the turn signal cam.
One is the hot wire that comes in from your flasher unit for the turn signals. It is the wire that supplies power to the individual wires that go to the turn signal bulbs. Only two bulbs (both on the same side front and rear) will come on when you move the cam to turn.
The second wire goes to the center tap from the brake light switch and connects to both rear turn signal lamp contacts. When you activate the brake light switch, it over rides the turn signal while leaving the front signal wire untouched. Since all 4 wires are individuals, you can have the brake light in the rear come on even with the turn signal in the turn position while the front turn signal keeps operating.
You just need to noodle this out and then identify which wire is which and I think you'll solve your problem.
I sure hope this makes sense and that it helps someone out.

My money is on a bad bulb.


Johnny

Way up under the bed I found a trailer wiring harness wire tied to the frame.

Lots of bare wire.

I cut the wire tie and let it fall away from the frame.

All works perfectly now.

So I removed the harness, it was pretty trashed and taped up the bare wire where it connected to the factory harness.

I wish every problem was that easy to fix.

Thanks to all.

Cool! Yeah, wiring problems can be a pain to chase down. Sometimes it's just about trial and error, glad it was so easy.