Turn Signal Running Light Connected?

Mechanogeek

Mechanogeek

True Classic
I have the following situation: All my tail lights work. Brake, running, reverse, and turn signals. ONLY problem I have is that when the right turn signal is on, the left running light blinks as well.

The left running light is on a yellow/red wire. The right turn signal is on a powder blue wire.

With everything disconnected (hazard switch unplugged, neither wire connected to the rear signals), I get continuity between those two very different circuits. Getting continuity between those two circuits would imply that the conductors from the two wires are possibly getting in contact somewhere.

I tracked the yellow/red wire to the fusebox (I think) after it passes through the loom connector underneath the dash. It looks like the powder blue wire goes to the same sort of loom connector under the dash, and then looks like it changes to a two-wire dark blue and royal blue pair, which I can't seem to track down.

Amy ideas where I should be looking?
 
I also would look at grounds (sounds like a floating ground). for Temp test take a jumper wire and ground the ground wire.
 
Previous fault diagnosis steps: Removed, cleaned, and reinstalled the hazard switch. Same issue. Disconnected all the other connections to the tail light housings. Same issue. Yep, I (think I) understand the whole grounding thing. I ran separate jumpers from the battery ground to the ground at the socket for the two bulbs (turn and running), and disconnected every other connection from the tail light housings. Same issue.

Further fault diagnosis... Trying to remove ground fault or bleedover from the equation.
With no ground wires attached, wires removed/unplugged from tail lights, hazard switch disconnected/removed, lights off, ignition off, unplugged the yellow/red running light wire, and the powder blue turn signal wire from the sockets, and tested continuity between the two wires, and still found continuity there. Am I wrong in my belief that there shouldn't be continuity between these wires normally? These two wires must be making contact somewhere? I need an automotive electrician (and a hug?).
 
Is there continuity to the right running light supply wire from the right turn signal supply wire? Or only continuity to the left running light supply wire to the right turn signal supply wire?

You are testing just the wires only, not at the socket?
 
Testing the wires only, not at the socket. Good question. Didn't think to test the right running light as well. Will check today. Thanks!
 
Mechanogeek said:
These two wires must be making contact somewhere? I need an automotive electrician (and a hug?).
Click to expand...
I can't give you a hug, but I can share a little insight... Sometimes it's best to think in terms of gremlins. It's useful, as you troubleshoot and do repairs, to pay your respects to the gremlins. Realize that as you fix one problem the gremlins will scoot into some other nook, and cause problems over there instead. Sound familiar? They don't like to be dissed, or even just ignored. You may wonder why I'm writing about fanciful creatures that remain hidden from most people's sight, but wreck havoc nonetheless. It's because I'm a freelance computer guru, so I know whereof I speak! :D Just about everyone can tell you stories similar to this one, taken from real life:

It was a typical cold, rainy, winter day in Northern California, and my '82 X would occasionally make this short, but loud screech. We're talking about fingersnails over the blackboard like screech, only louder. "SCREEEEEECH!!" It sounded like I was slamming on the brakes, trying hard not to hit someone, but it would happen, randomly, even while the car was waiting for a green light to appear. I don't like it when my cars look and feel old, or do things that remind me that they are old. My cars ought to remind me of the fun and joy of living, not the specter of decay, and mortality. This screeching had been happening a couple of years in a row, and always started when the rainy season started. That was a good clue, but not good enough. I checked the alternator belt, tightened it, replaced it. I even replaced the alternator, thinking a bearing might be going bad, but nothing made the random screeching go away. I took the car to Benedetti, to see if they could track down the problem. You can probably guess what I'm about to say next, because I'm almost certain something similar has happened to you, too. Of course my '82 X didn't make even a peep the whole time the folks at the repair shop were looking at it. Problem unsolved, I drove my car away. You can probably also guess that it made a loud screech just as the repair shop was out of sight, which is exactly what it did. It's a well-known fact that gremlins love to hide when technicians are around doing their poking and probing. You can almost put betting money on gremlins, and could make a decent living gambling on their antics. Except that nobody in their right mind would bet against you! And, yes, this happens to me as a computer tech, too. A computer will behave beautifully on my workbench, and be the picture of perfection. Back home, or back in its office -- not so perfect after all. I hope you'll forgive a momentary digression: One of my clients had a small Dell tower, which refused to boot up. I took it home, to diagnose on my workbench, and found it worked great. It had no flaws as far as I could tell. Back at my client's home the poor little thing still would not boot. WTF? It was her old Lexmark printer. As long as its USB cable was unplugged, the computer would boot up just fine. Plug the USB in afterwards, and the Dell was still happy, and the Lexmark would still print just fine, too. There was something amiss with the USB circuit in the old Lexmark -- not enough to make it fail, but enough to cause problems -- that's where the gremlin was hiding! Now back to my '82 X... It was pointless to turn around and bring it right back to Benedetti. We all know what would have happened -- we would have heard the crickets chirping, it would have been so quiet. I finally got the solution from an unusual source. I bought a second X1/9! My '85 Bertone still had a water splash guard between the road and the alternator and its rubber belt. That prevents too much water spray from reaching those areas, and making them slip, maybe even screech? Yes, indeed. My '82 had the correct mounting holes for the splash guard -- even had the metal part of it, bent upwards, out of the way -- but it was missing the important plastic and rubber pieces. Since I was not planning to drive the '85 in the rain anyway, I let my '82 borrow the parts from my '85, and then my daily driver no longer screeched when it started to rain. I was happy, the gremlins were happy (they're currently hiding in one of the 7.5A circuits of my '85 Bertone, and some of their cousins are in your turn-signal wiring, too). I wish you much luck, and assured success!

EDIT: Speaking of gremlins, when I was a boy I loved the AMC Gremlin X! Here's a photo of a 1977 example. That happens to be the same year I started lusting after X1/9's instead. You could say that's when the Gremlin X became my ex. The true X romance would begin 20 years later.
1977_amc_gremlin_x.jpg
 
Last edited:
Have you noticed if the side marker lights also blink with the turn signals? There is a mod many people make to have the side marker lights blink in unison or opposition with the turn signals so the turn signals are effectively attached to the wiring for the running lights, all the running lights.

Something to look at.
 
Another possibility is the wires are making contact somewhere due to failed insulation. I found several places around the wire harnesses where the insulation had been compromised. Things like dry brittle insulation that was cracked and/or chipped away, or the insulation had rubbed against something for so long it wore through, or similar. It would be unusual for two wires to do that and contact one another but it can happen. More likely in places where the wires are exposed or near heat sources, but also at the points where the harnesses pass through metal panels. One of the failures I found was where the main loom passes through the rear bulkhead (between passenger compartment and engine, at the spare tire well), where it wore through the grommet and the wires' insulation.
 
Your suggestions so far have been appreciated. I am still working on the diagnosis. It would appear that the two wires in question may in fact be grounding through the chassis somewhere (Dr Jeff). I can get continuity to chassis ground through both of the wires in question, but not from the other rear lights. I went so far as to make sure that none of the wires in the front of the car were in contact with anything, thinking that there might be some cross connectivity from one of those connections as well.

My other problem right now is not car-related. The temperature is about 95f outside, and about 5-10 degrees warmer in the garage. So, I'm done for the day, and probably a couple more. I'll wait and ponder until I can get a sub-85 degree day to further explore the wonderful world of wiring.
 
Mechanogeek said:
I can get continuity to chassis ground through both of the wires in question, but not from the other rear lights
Click to expand...
Did you check that with the wires disconnected from the sockets? That sounds a bit odd because if the wires were shorted to ground you would likely be blowing a fuse, etc. So you might be seeing some continuity feeding through the light filaments to ground? Let us know more when you get back to it.

[Add 15-20 degrees and that's what I have to deal with. But my smaller workshop has a little air conditioner that makes it possible to do some jobs inside. Still not fun for a guy that spent all my life on the Calif beaches before coming here.]
 
All of my checking in the last two days has been at the wire connector, disconnected from the sockets. Isolate the wires and reduce the variables. I wanted to make sure the sockets were not part of the problem, and the connectors and grounds were not part of the problem, and that the only thing I am checking (hopefully) is the power wire continuity.
 
Perhaps you already said that, sorry. What seems strange to me then, is that you are getting continuity to ground for a power lead. That would cause a direct short and blow a fuse or cook a wire, etc. Unless these are not the power wires...honestly I don't know the colors for all this to tell.
 
I found something out that puzzled me. on my 86 x1/9 I replaced some missing bolts on my cooling fan for the injectors (installed one that was too long) and it went in and pushed on the power feed for the left turn signal. The only symptom was the left turn would not work, did not blow a fuse, (and they were working before I started working on things). Not blowing a fuse, it never occurred to Me I would have a dead short. I took everything apart that I had worked on that day. (was a good productive day I worked on a lot of things) and of course, pulling the fan was the last thing I opened back up. and there was the issue.

Not sure why it was not blowing the fuse, It should have.

I don't know if this little story is of any help or relevant, but worth mentioning.
 
Rod Midkiff said:
I don't know if this little story is of any help or relevant, but worth mentioning.
Click to expand...

At this point, if the story involved little blue bunnies from Mars, I'd still find it relevant. I am going to be disconnecting the wires for the tail lights from the fuse block, then test to see from that end of the wire if I still get some grounding, and then running some temporary wires from the fuse block back to the tail light, if I don't find a grounding issue. If I have to re-loom the back end of the car, then so be it. Those old wires are dirty and grungy anyways.

The grounding I am getting does not seem to be a LARGE amount of contact, not enough to set off the 'beeper' for continuity on my tester, BUT there is still SOME continuity there. Hopefully just replacing one or two wires will help solve the issue.

I'll know more tonight.
 
Mechanogeek said:
The grounding I am getting does not seem to be a LARGE amount of contact, not enough to set off the 'beeper' for continuity on my tester
Click to expand...
That helps explain a little. If it's not a solid short but only a slight contact between the wires (like insulation is rubbing through), then perhaps there is enough current passing to actually blow a fuse. Like Eric said, other components are also limiting the current. And the turn signals are an intermittent operation, only on for a brief moment at a time. So not enough heat builds up to do real damage. All just thoughts and theory though.

In repairing the numerous electrical faults on mine, I found the quality of the wires and connectors was not the greatest (at least compared to other vehicles in my experience). The installation of the harnesses was also less than stellar; allowing things to rub unprotected, wires that were crushed by other large components bolts over them, etc. It would be quite a task, but maybe see if you can expose the two wires in question their entire length. Looking for faults.
 
You must log in or register to reply here.
Back
Top