Hey guys I'm working on a 68 cutlass S and I'm having some funny thing happen when i step on the brake. So.. when i hit the brakes the dash lights, front markers and front turn signal light all come on?!?! Another thing that happens is when the lights are off i can get the right turn signals to work right and then the left ones will flash but will also dimly flash the rest of the marker lights and signals… then with the lights on i get the right turn signal to work but no response from the left the left one when i try it. Talk about a wiring demon huh! Thoughts? Solutions? Ideas? Im lost on this one. I was able to track down a few mice nibbled wires and bad grounds that i have fixed but still didn't solve all of the issues. HELP PLEASE

 

Bad ground in a taillight socket, most likely. Go through them all very carefully.

Welcome to ClassicOlds.

- Eric

 

ok doesn't the tail light socket ground itself via the actual taillight it self or is there a separate ground wire?

 

It should ground through the bumper, but a little bit of corrosion one place or another, including inside the light sockets, is all you need.

- Eric

 

Eric, isn't there a small ground wire
attached at the base of the trunk catch
coming from the rear harness?
Just going by memory, so I could be WAY
off on this.

 

Could be. I'm honestly not an expert on '68s.

- Eric

 

there is what i think is a ground (black wire) from the left maker light that runs to the other side which is in good shape with good connection. i think i need the right wiring schematic which I'm having trouble locating, i think it may help

 

That's easy.

Just go to WildAboutCars and download the Chassis Service Manual for free.

- Eric

 

They say go to wildaboutcars.com to find the schematics.
I have a hard time navigating there. Good luck with it.

 

How does the turn signal / hazard switch in the steery column feel? Anything odd or broken about it? Most of those wires meet at that switch, and if it gets broken or wires wore thru and shorted, you may get symptoms like that.

The intercloud is great if you can find your way to what you need, but remember you can still get a paper with a paper colored diagram. '68 issue manuals are always falling apart though.

Diagnosing bulb ground faults can be aided by removing bulbs or entire sections of the circuit [trunk connector to everything aft of that for example] and then see how that affects the issue. If the issue goes away, then the cause was in that section.

1968 Taillights are installed in the body, not the bumper. The backup lamps are in the bumper, and the plate lamp.

 

Thanks Octania.

I could go through why I think it's a ground (after I remember exactly why, myself), but I'm at work now, I'm busy, and I'm on my phone, so I just can't get fully into it.
I even posted a lengthy explanation of it once, though I don't recall the name of the thread.

It is always reasonable to check the switch, though

- Eric

 

the turn signal switch does feel different from left to right so that may be my issue but i will be thoroughly checking my grounds as well. thanks for the help guys!

 

First check to see if the rear bulbs are the correct two-pinned base ones and that they are screwed in all the way.
If a single pin bulb was used, or the bulb only screwed in part way, the two pins in the socket will be shorted, causing the brake circuit and running light circuit to be shorted together, causing a similar problem to what you have.
I have also seen the two bottom pins on correct bulbs "mash out" or mushroom due to the pressure of being seated a long time, AND being too soft a material (defect).
Does the '68 have parking lights in front or are they turn signals only?

 

Rob I owe you a case of beer! One wrong bulb! i was just about to start pulling apart the whole wiring harness to search for the problem but i saw your post just before that. Thanks a lot dude now i can get the car inspected and on the road on monday! Big ups to you

 

Excellent, Rob! Sometimes I miss the simple stuff.

- Eric

 

AWESOME! Glad I could help and that it was an easy fix.
Just do not ask how I figured out to check this first...
Sometimes even auto parts stores will sell a bulb just because it can fit into the socket and perhaps even stays in there...
Now - carefully funnel the beer into the USB port on your computer and attach to an email.................