My 1976 Cutlass Salon has an odd tail lamp turn signal issue. The upper bulb of left lamp flashes brightly while the lower bulb is much darker while the lower bulb of the right lamp flashes brightly and the upper bulb is much darker. That's the best way I can describer it; please watch linked video below to see it happening (file was too big to attach to this post so I had to post it on YouTube).
https://www.youtube.com/watch?v=qzXk...ature=youtu.be

I use Sylvania Silverstar bulbs which I installed early last year (so they are not old). The only things I have done to the car electrically in the last year were to replace the column-mounted dimmer switch, install an electric choke, replace the HVAC control switch and replace the HVAC blower relay --- in that order. The only one of these recently done was the blower relay.

I don't want to "tear into" this without a bit of input from those who may have some experience with this. My only experience with this sort of thing occurred many years ago with Chrysler products --- back then, it was almost always a ground problem resulting from poor electrical engineering or neglect. With the exception of the dimmer switch, I have not found under-engineered electrical system issues to be a problem with this car.

Jeff

 

What do the lamps do when you apply the brake?

 

It's most likely an issue with the sockets. I had something similar to this when I owned my 76 Salon 28 years ago and I just replaced all of the sockets and it fixed the issue.

 

The same thing, Eric; ditto when I use the turn signals individually.

I forgot to mention that, every once in a while, one of them spontaneously reverts to behaving normally --- so the stupid problem is intermittent!

Jeff

 

Check the grounds on the tail light harness, and clean the electrical connectors on the harness.

 

^^^THIS. This is the classic bad ground with an 1157 bulb. Do the turn signals behave differently if the tail lights are on vs. off? The 1157 bulbs have two filaments with a common ground. If the ground connection is bad (and this could be where the spring-loaded socket snaps into the tail light housing), the turn signal filament will ground through the tail light circuit, causing both filaments to illuminate. If the tail lights are on, the turn signal won't work at all, since now you have 12V on the other side of the filament instead of a path to ground.

 

This is a convincing sign of poor connections and/or bad grounds.

 

Jeff,

I had the same issue with my 76 tail lights. They would turn into the tail light housing but they were a tad loose. If I really turned them as tight as I could they all illuminated just fine, however hit a few bumps going for a cruise, I found that some were dim and not working properly.
I ended up bending out the 3 prongs on all 4 sockets, then turning them into the tail light housing.
Just test fit by prying the prongs out until you get then to be a nice tight fit.
I hope this helps
Eric

 

Okay; thanks, guys.

I guess that I didn't remember that the lamps grounded through the socket itself; for some reason, I thought they grounded remotely and was supposing that there was some "central issue". I'll clean/bend the grounding tabs tomorrow.

Jeff

 

FOLLOW-UP

Tail lamps are fixed. I simply bent the contact on the ground jacket (into which the bulb fits) so that it would positively contact the tab on the ground wire (coming from central grounding source --- so I did remember correctly) when the socket is screwed into the lamp housing. Why didn't they simply solder these two items together to begin with?

In any event, all lamps now work properly (finally --- nothin' gets done fast around here!). Thanks for all of the help, gents!
Jeff

 

Because that would have added a lengthy labor-intensive process to the assembly of the vehicle. Time is money (and thus profits) in mass production. The car only has to work until the warranty runs out.

 

Thanks for the update Jeff!! If you get a chance, could you post a short after video with a link here. That would be great if you could for all the 76-77 guys.
Cheers
Eric