O.K. quick review:

Turn signals work fine with NO running lights on. Turn on running lights/head lights and left turn signal continues to work fine, right either does not work or very slow blinks.

So before we go on about bulb, socket, blinker. It will do the very same thing if I unplug the 4 wire harnesses on the left and right fenders going to the front AND rear is completely unplugged. Dash cluster removed... same thing.

I have the entire dash apart and have inspected all the wires behind the instrument cluster and exiting the firewall. They do not appear hacked or in poor condition. I have swapped flashers, same thing. I have also removed and inspected the headlight switch. Nothing jumped out.

My next step is to pin test the TSS and Headlight switch. Before I go through that pain. Anyone have a concrete thought?

I found a guy on Youtube goes by the name Dusty Miller, with a "our" vintage truck with the EXACT SAME issue. But of course the video is over a year old and there was no notes left as to what the fix was.

Advice would be greatly appreciated. I am thinking it will end up being the TSS, but would love a pin test procedure for it.

Rayo

 

Might be worth replacing the light switch if it is original.

 

Read these yet? https://www.ford-trucks.com/forums/1...ml#post1812190


Turn and Stop Lamp Diagnosis for 70's Ford Pickup - Ford-Trucks.com

 

I had found the top one, the bottom one is pretty much what I am after, a pin test procedure for that connector going to the TSS. My connector has a few more wires then the 7 listed but it should get me started. I also have the wiring schematics for the truck... hopefully I can figure it out.

 

Before you spend too much time pulling apart all the hard stuff, you may get better traction by checking your grounds. When the grounds by the lights get flaky, all kinds of odd things happen, often at seemingly unrelated parts of the lighting circuits. Make sure all your grounds are good and you will have a far easier time troubleshooting.

 

Hi Dave,

Thats just it, I can pull the harnesses apart at the fenderwells, essentially taking the grounds out of the mix and experience the problem with a test light or just the dash turn signal indicator. And of course I know I have good ground with my test light.

After more searching last night and doing a pin test on the horseshoe connector I have ruled out the TSS. It passed all the tests with no continuity where there should NOT have been.

Now the interesting thing... on the feed side of the horseshoe connector (coming out of the main harness) I was testing feed pins and found one that has a low voltage bleeding through it. Enough to dimply light my test lamp. That is the White with Red Stripe wire, it starts at the fuse panel position 8 and hits connector 805, which is guess what? Yup the Emergency Flasher connector. From the flasher it goes to C-305 which is the male pin side of the horseshoe connector.

Sooo anyway, I pulled the emergency flasher and swap it for the turn flasher and I no longer get any bleed through to the W-R wire. Makes the emergency flasher VERY suspect. I thought they were both good, but the Emer one is very old original looking. Soo running to the auto store today to get two new ones just to cover my bases. I am hoping the bleedthrough from this flasher is the root of evil. What I can't figure out is why does it only affect my right side vs. left side. I did check all my left, right, front, back for any continuity to ground. And luckily found nothing indicating a short. Also checked for any continuity between left and right, left, right and running etc. All tested good.

Will report back with the results of the new flashers.

Rayo

 

I did not want to be one of those posts that someone comes across in a future search that says "That is exactly my problem, what did the guy do to fix it?". So all my stuff is fixed and here is the detail:

Not sure I originally mentioned it but in addition to my turn signal woes, some of the instrumentation lighting in my dash had stopped working on the right side. Pulled all the bulbs lightly cleaned the traces in the plastic membrane with a soft wire brush... cleaned the bulbs contacts that same way. Spread the bulb contacts out for more pressure. Put it all back together, it all works great.

Now for my turn signal issue. I originally thought it was for sure the TSS or Headlight switch. But all my testing kept clearing both those items. I did replace my flasher with a LED one, which strangely let the right side blink properly... but I would still have an issue where when you would turn the headlights on, the right turn indicator on the dash would dimly glow. And turn signal operation on the right side with running lights on was intermittently working at best.

So back to the front to investigate some more. I took the front ground on teh passenger side core support off and wire brushed... that was not the problem. Then I started to look closely at the socket, which I previously tested the wires going to it, but stuffing the meter lead in the back side of the wire.. it test good.

But thinking I must be going crazy, I tested directly from the fenderwell connector to the actual contacts in the socket. Whaddaya know... the ground lead in the socket is NOT making a connection. Right in the plastic socket where you have no way to take it apart, the wire is good at the outside, but does not make a connection to the ground tab on the inside, side of the socket. So a trip to that autoparts store, two sockets (one for each side) and all is well.

Yup.. as other said, check your grounds, but also verify those 30+ year old sockets are actually good.

 

Glad to hear you got it figured out and thanks for the detailed repair report.