Wiring turn signal question, purple wires

[Peepaw]

Originally Posted by BigBird05

The ign switch pigtail in your truck doesn't have the Dk green wire for the temp light cir. bulb check. I am guessing you have a gauge. The aftermarket pigtail does.

That is correct, I do have the gauge.

I am calling it a day today and will get back at it this week and keep yall updated. I know its something simple and Im just over looking it right now.


Thanks again everyone for yalls help

[Peepaw]

OK, late last night, I went BACK into my garage and found a potential problem.

For the FRONT turn signal lamps, there is a dark blue and purple wire. Factory there is a dark blue (right hand) and purple then there is a light blue and purple (left hand).

Well, when the aftermarket lamps got there, they both have purple and dark blue wires.

Well, I ASSUMED the purple would go to purple, and the blue wire would go to light blue on one side, and the dark blue on other side.

Well, I grabbed my old turn signal lamp, and it WORKED. So I was like, WTH?!?!?!? My new lamps are already burnt out?

So, thats when I started looking at teh wires, and was like, well, what harm is it in flipping purple to blue, and blue to purple. Makes sense right?


So, I flipped the wires and BAM. Front turn signal lamp worked just fine.

I did NOT check turn signals/rear and or brake light.

It was late, and I felt like I accomplished something so went and took a shower and to bed.

So, im HOPING (once again) that I have found my problem.

I still think I will have a brake light (left side) when I turn right side blinker on but Im pretty sure I have figured out why my front turn signal lamps are doing what they are doing.

I'll get back at it this evening

[Peepaw]

Update:

I was not able to take a look at truck last night. Was at my sons baseball practice until late.
Got baseball again tonight and tomorrow night, so will be @ Thursday or Friday before I can check it out.

I will keep yall updated.
Thanks again to everyone that has chimed in given info and helped out.

[Peepaw]

Ok, update.
Baseball got cancelled so Im working on the truck.

EVERYTHING WORKS. Almost.

Got headlights, front turns and parking lights working. Beautiful.
The rear brake lights perfect. Rear parking lights perfect. Blinkers perfect with lights on or off.
Brake lights work with LEFT turn signal on.

The ONLY problem Im having now is:
Brake pedal on, and RIGHT turn signal on (right side blinks), but my left rear brake light goes out.
Thats IT.
Thats ONLY problem Im having.

Its new socket and bulb. Just dont believe its ground issue. Have battery cables attached to rear frame and the bed. Checked for ground and we’re good.
Got ground from battery to frame up front.
Have couple other wires @ 12 gauge just for redundancy from negative battery terminal to frame and core support.
All told, I have 7 grounds. Way over kill.
I checked for ground at tail lamp assembly. We’re good.

Turn signal switch??????

[pjmoreland]

If you own a steering wheel puller, pull your steering wheel and then pop the top plastic portion of your turn signal switch off to see if the contacts are dirty. They might just need to be cleaned.

[pjmoreland]

See this thread. Same issue

https://67-72chevytrucks.com/vboard/...d.php?t=822068

[Peepaw]

Originally Posted by pjmoreland

If you own a steering wheel puller, pull your steering wheel and then pop the top plastic portion of your turn signal switch off to see if the contacts are dirty. They might just need to be cleaned.

Roger that. Im pretty sure thats what we are going to find. I have isolated every wire. Ran ohm test on every wire from light switch to each light source and from “u” shaped connector to ignition switch, light, etc...
No breaks in any wires.
Every bulb is new. Every light socket is new. Headlight switch and ignition switch new.
The only thing not replaced at this time is turn signal switch and dome light (it works).
To be clear, I didnt buy all this just throwing parts at it. I did it because the truck needed to be rewired and most of the sockets were in poor condition after 45+ years on the road (shes been under the knife the last 4-5 years ).
She has had some serious TLC over the years. New paint. Suspension. Brakes. AC was ever reworked. Etc....
Really only thing original to her was frame and 80-85% of sheetmetal is original (bed was replaced @ 35 years ago and Ive done new cab corners and rocker panels)
But wiring had weathered and had been neglected, cut, spilced, etc....
So it was time for the wiring to be updated.

[pjmoreland]

Very cool. It's gotta be satisfying getting toward the end of the project!

[BigBird05]

Check to see if the tail light wires are in the right location in the socket. Sounds like a back feed cancelling out your left light. Or your right light is trying to get a ground thru the left light bulb filament.

[Peepaw]

Originally Posted by pjmoreland

Very cool. It's gotta be satisfying getting toward the end of the project!

Indeed sir. Im getting there. This truck was put together May of 72, same month and year as me.
Then, on back of instrument cluster, a 4/27/72 stamped on it.
My son was born in the 4th month, my daughter was born on the 27th and I of course born in 72. Got some nostalgic going. 😳🤣

[Peepaw]

Originally Posted by BigBird05

Check to see if the tail light wires are in the right location in the socket. Sounds like a back feed cancelling out your left light. Or your right light is trying to get a ground thru the left light bulb filament.

Im gonna pop off turn signal switch (have new ome ordered, just gonna go ahead and install the new one), and Ill check the other items you mentioned.
Very close indeed

[pjmoreland]

Originally Posted by Peepaw

Indeed sir. Im getting there. This truck was put together May of 72, same month and year as me.
Then, on back of instrument cluster, a 4/27/72 stamped on it.
My son was born in the 4th month, my daughter was born on the 27th and I of course born in 72. Got some nostalgic going. 😳🤣

Haha, nice. It's easy to get attached to one of these trucks when you spend so much time working on it.

[pjmoreland]

A quick test of the turn signal switch would be to see if you have continuity between the white wire (power from brake switch) and the yellow wire (left brake light) at the U connector when your right turn signal is turned on.

[pjmoreland]

Another way to test the turn signal switch would be to plug your new one into the truck harness loose under the dash and see if it fixes the problem.

[Peepaw]

Originally Posted by pjmoreland

A quick test of the turn signal switch would be to see if you have continuity between the white wire (power from brake switch) and the yellow wire (left brake light) at the U connector when your right turn signal is turned on.

I have not checked that. Will give that a looksie. Thank you

[Peepaw]

We had baseball late last night, so didnt get a chance to get any work on the truck. Will check turn signal switch tonight.

[aggiegrad]

I am pretty sure that you will fix the brake light issue by changing out the turn switch. I was skeptical but the $40 ac Delco switch fixed the problem and seemed high quality. I started to try to clean the old one first but I am glad I just replaced it. the old one was really loose and wearing out through the years. The only issue with the new switch is that it has a newer looking round hazard knob in stead of the old red lever. They also have an adapter that fits the u shape plug as the switch is more universal now.

I will say that the shifter is much smoother as well now as I was able to grease everything while putting it back. I am glad I spent the time. There was a good youtube video that I found that walked me though the process of changing it out.

Let me know if you have any questions. If you are in Pearland you really are not that far from me.

Bryan

[Peepaw]

Originally Posted by aggiegrad

I am pretty sure that you will fix the brake light issue by changing out the turn switch. I was skeptical but the $40 ac Delco switch fixed the problem and seemed high quality. I started to try to clean the old one first but I am glad I just replaced it. the old one was really loose and wearing out through the years. The only issue with the new switch is that it has a newer looking round hazard knob in stead of the old red lever. They also have an adapter that fits the u shape plug as the switch is more universal now.

I will say that the shifter is much smoother as well now as I was able to grease everything while putting it back. I am glad I spent the time. There was a good youtube video that I found that walked me though the process of changing it out.

Let me know if you have any questions. If you are in Pearland you really are not that far from me.

Bryan

That is what I am thinking as well. I hope to have the turn signal switch diagnosed properly this evening.
I get off work at 6:00, home by 6:20, have baseball at 7:15 tonight.

So, have @ 15-20 minutes to check signal switch.
If not tonight, definitely tomorrow (and my new switch should be here today/tomorrow as well), but Id like to test old one (now that I have been given info on how to test it) so I can compare notes with new one.

But I have taken every single light/lamp, and gone directly to them and tested them, and they work (correctly wired up).

So we'll see soon enough.

[Peepaw]

OK, I power probed the green and yellow (and every wire for that matter, AGAIN) wires at the U connector. I am DEFINITELY getting different readings from the two. I shouldve taken video of it. But it's doing something differently when right turn signal is on and brake lights on then it is with left turn on and brakes on.

As luck would have it, my new turn signal switch came in this evening while I was at baseball practice. Sooooooo, I've got work tomorrow and will install new switch after work, OR wait until Saturday morning.

I will keep everyone updated and in the loop. Thanks guys.


Oh, my new Holley Terminator X came in the mail today and so once I get this basic wiring up, I can install the Holley and get this bad girl back on the road.

[pjmoreland]

If you were to unplug the turn signal switch U connector from the harness, then you could measure the resistance between the white and yellow wires of the switch when the switch is in the right turn position. You should get a nice low resistance reading.

For comparison, you could put the switch in the left turn position and measure between the white and green wires.

If your multimeter has a continuity setting where it beeps when the probes are connected together, use that setting.

[Peepaw]

Well guys, we got her!

It was turn signal switch. All this head scratching, and bouncing ideas' and going absolutely mind pulling hair out crazy, it was turn signal switch.

I have been doing this long enough (albeit, wiring is NOT my thing) to know to never assume anything and I assumed it was something I had done (in the process of wiring the truck up).

I was 90% done with the wiring, had it all looking great, routed properly, etc...to only pull EVERYTHING apart thinking it HAD to be an issue with what I had wired up.
What makes matters worse is that I had bought everything for replacement (bulbs, headlight switch, ign switch, new fuse box, all new wiring from front to back and the ONLY thing I had not bought was turn signal switch.
Why on earth did I not buy one while I was in the process of doing this?!?!?!!?
My only explanation is that it was to teach this old man something, or drive that point home even further, NEVER assume anything.

I appreciate everyone's input and advice. Id say 99% of what was told to me was put to use. I listened to everyone, and in doing so I DID find some small mistakes I had over looked (ground cable/wires...needed better ground for sure).

But again, thanks again for all the input.

I do have a build thread going, and I am going to get some work done on her this weekend and will have some more updates and pictures of teh process.

[pjmoreland]

Whew! I was getting a little nervous after you spent money on a new switch. I'm glad it worked out. I will check out your build thread.

[poseidon.beard]

This thread has lots of good stuff.

I had problems with my 70 suburban and by searching the threads, taking in all the possibilities...went after it. The wiring diagrams, period specific, that someone posted helped tremendously. Turns out, I had two issues.

1. The brown wire coming from the ignition switch to the fuse panel was plugged in the the wrong terminal. Resulting in no power the fuse block nor the flasher. Transferred (Brown & Brown/white) to the correct terminal and got the 12v I needed. (kudos to the wiring diagram!)

2. Tested the turn signal and noticed the front signals were correct but the rear lights were opposite. Re-pined the aftermarket turn signal switch u-shaped harness, swapping the green for the yellow and yellow for the Green, and BOOM. It worked flawlessly...

Thanks fellas and hats-off to those who put their experiences on these here forms for others to learn from.