Let me first say that I have just about every fuse out of the car except the DIR SIG 20A fuse. I also have pretty much every gauge disconnected in the console.

My problem is that the drivers rear turn signal is very dim when I turn on the signals. The front left/right and right rear turn signal lights all look correct as far as their light intensity.

Has anyone run across this before?

Like I said, maybe it has something to do with all of the other stuff I have disconnected, but it seems odd that it's just the left rear that is acting strangely. At first I thought it wasn't blinking at all until I looked closely and did see a dim glow.

 

Sounds like a bad ground to me

 

Almost always a bad ground.

 

Or the wrong bulb.

Probably going to find it wont work at all when the TL are on.

 

So I spent about 2 hours this evening trying different things with no conclusive decision yet.

I did have one thought but it backfired on me. I'm using 1157 bulbs which have the two nipples on the end: one of which I assumed was for the turn signal, and the other one for the parking brake. Then of course there's the outer case which I assumed leads to ground. So my train of thought was that if I do a continuity test across the two nipples I shouldn't get a connection, but how wrong was I.

I had only imagined I'd get continuity from one nipple to the outer case, never just across the two nipples. Since they had China marked on them, I thought I'd go to Walmart and get some Sylvania 1175 bulbs to make sure that wasn't it. Nope, same thing.

At this point, I completely disconnected the ground on the right rear housing so there should be no way that the case is grounded. I left the brake/turn power connecter connected and had a bulb in. At this point, if I turn on the right turn signal, I thought the light would not come on, but it did at about half brightness. So somehow the turn signal wire, I believe it's dark green on the right side (+) and yellow on the left, must be grounding through the brake wire.

So I need to step back and rethink the problem some more. I'm almost to the point of pulling the whole rear wiring out of the car.

 

When you don't have the socket grounded the brake filament tries to find a ground. It finds it through the parking light filaments of the other lamps. It has high resistance. Thats why it is dim. Fix the ground and you will fix the problem.

 

I just purchased a 68 convertible and had the same problem when I checked the brake and tail lights. A couple of them were dim. The brake lights were not as bright as the others. I removed everything and did pretty much what you did...ohm out the lights and connectors...I felt I was going around in circles. When to Pep Boys and got some new 1157 bulbs. I got under the car and even though the grounds were connected I removed them, cleaned the surface of the ground cable lugs and the housings they attached to and all is good...hopefully this helps...Brent

 

I think what I'm going to do tomorrow is that when I put the bulbs back in, I'm going to insert some wire between the socket wall and the bulb grounding case and run that wire directly to a good ground.

I think that should at least rule out whether or not the casing is the cause of the bad ground or not.

After clearing my head for a bit, I know understand why I had continuity between the two nipples. It's pretty obvious why there's a path from one nipple to casing back to the other nipple that going to the same casing. I had been staring at the problem too long.

I'll be back at it tomorrow.

 

That will be a good test! You can run a wire from a good ground and touch the outside of the bulb socket, that will tell you if the original ground is good or not.

Hope that fixes it!

 

Corroded grounds. Just bite the bullet and take them all loose, clean them, good, reassemble and shoot some semi-gloss black paint or black undercoating over them. You will save a lot of 'grief' just taking a morning [or the entire day] and doing that to all the underbody grounds.

 

Great idea...I am awaiting delivery of my assembly manual so I know where all the grounds are...

 

I found that the housings had a mild layer of corrosion so when I touched the ground wire to them the lights did not light up like they should. I used a Scotchbrite pad and gave them a good scrub....all is good now...Brent

 

So my head is still trying to wrap around exactly what's wrong. The fronts are still working perfectly. I've taken sand paper to the wire harness grounding connectors to make sure there is no rust there.

Now when I turn on my left turn signal, my left lamp goes on but so does the right lamp to a lesser degree. For my left lamp I just bought a new metal housing for it and wired a 16 gauge wire from the back bolt directly to the negative post on the battery, there is almost no way a better ground can be found.

So if it's not the ground, what else can it be?

Tomorrow I'm going to separate the rear harness and attach a wire directly from the battery (using inline fuse) to the single wire harness input wire and see if I still get the same problem. If I do, would that almost certainly mean that there's some kind of short in my wiring harness? Because at that time, I've bypassed everything except the harness as there's only: wire from positive battery term to single wire in harness, and turn signal housing ground wire to negative battery terminal.

I'm also wondering if it's possible the nuts I'm using on the housing bolts aren't metallic enough and are acting like resistors. ?

 

Isn't 12 volts fun ?

 

I've always heard of electrical gremlins in systems that they're hard to find. I was just expecting with the vettes relatively simple layout, that it wouldn't be such a big issue.

I've searched on Google and I know that I'm certainly not the first one to have this particular problem with my vette.

 

You are not the first one and you won't be the last BUT the solution will almost always be the same,the ground as Wombvette referred to.

I didn't read through your thread thoroughly but I did see where you said the right is now coming on,I would suggest removing the right bulb and focus on the left until you get it grounded and working correctly then move to the right.
Grounds grounds and more grounds..

 

Most assuredly.

When in left turn signal mode, the left is blinking at what looks to be full power, except that the right side is on but much dimmer. I also noticed that my license plate lamp is dimly blinking along with the right lamp. It seems if I let it go long enough, that the license and right lamp get dimmer almost to the point where they're not on.

As for grounds, in my post just above, I was hoping that my new 16 gauge wire going directly from the housing bolt on the left lamp to the battery negative terminal would solve it. I can't see how I could get any better ground than that.

I'm still wondering a bit if my bulb outer casing is making correct contact with the lamp housing as it seems a bit loose when I plug it in. I'm trying to find a way to make sure that connection is solid.

I've thought about trying to burn out the 2nd brake filament in my left lamp so that there's no way that power can get back on the other circuit. If I still get a blink on the right lamp, that would allow me to verify that the problem is in the wiring harness as there would have to be a short in there to now get power to the right lamp.

 

I ground a long piece of wire and touch it to the bulb case.

 

Check out this thread and scan down to post #17 . I posted some pics of why the sockets lose ground.
http://forums.corvetteforum.com/c3-g...n-signals.html

 

So, I pulled my turn signal switch to see why my hazard pull wasn't working. Well Bubba hadn't connected the rod from the hazard pull to the switch in the correct opening so it wasn't doing anything. Not sure if that alone would have possibly shorted out something if the rod was touching the back metal plate of the turn signal switch or not.

Anyway, moving on to the front lamps that I *thought* were working and noticed that my left lamps were slightly blinking. So I created this video to try and describe my problem.

#1 Rear lamp harness is disconnected.
#2 Turn signal switch is disconnected.
#3 Light swith is connected and the parking lights are on, but not pulled out all the way to turn headlights on.
#4 The RH lamps look to be fine (no blinking)
#5 new hazard flasher installed (model 522 I believe)
#6 new turn signal flasher installed (model 522 I believe)
#7 I've tried running a 16 gauge wire directly from battery negative to the yellow bulb housing to make sure that's not the problem; it didn't solve it.

Here's the video.