I've been dealing with what seems like a grounding issue for a while now and can't seem to track it down. 1995 LT1, manual.

If headlights are on OR if I press the brake, my turn signals do not function. Further, pressing the brake seems to cause the cluster to react (RPM needle drops), cluster lights dim, etc.

This seems like a grounding issue. I have done the following:
Replaced all exterior bulbs
Checked ground @ headlights
Tried running a better ground to the battery
Spliced into / ran a new ground under the steering column (D3 I think it was? The thick black wire, goes to driver side pillar)

What is there left to possibly replace or check the ground on? Any help would be appreciated, particularly if you can include diagrams or pictures. Thanks!

Incorrect bulb(s)in rear sockets? If you turn light and hazards on the same time. Do lights operate correctly? If not look at malfunctioning lamp.

The bulbs are correct, and the turn signals, hazards and the likes all function properly so long as I don't press the brake pedal or turn on the headlights

So if you have parking lights on with hazards everything works correctly? Headlight circuit has nothing to do with park light circuit.
Parking lights use brown wires
Turn/ brake lamps use blue or green wiree
They use a common ground, failed socket grounds causes feedback. Pressing brake current is sent through turn signal switch to tail lamps using turn signal wires. There is a separate circuit to high level stop apart from turn signal switch.

From video that strikes me more as as short or bad cluster then grounding problem. I think the only way you can fix is to remove the cluster and look it over for problems, check the wiring running to the harness. Here is ground harness on my 96 which I don't see would be different from 95. If I recall G102 is the ground for the cluster panel, might want to check that one.

Oh! Switching on the parking lights -does- stop the turn signals / hazards, just like hitting the brakes or turning the headlights on.

So you're saying it could be a grounding issue with one of the bulb sockets? Or the common ground point they feed into?


@bac22
I haven't actually checked G102 in your diagram, missed that one. Cluster issue could very well be the case too. How is it accessed?

Your losing ground somewhere. I would check sockets ground terminals.

Is there a good way to do this without it taking forever? Like would certain sockets be more likely than the others, and how do I check the socket grounds?

Tail light harness has common ground at right halo. The front lamps ground on each front frame rail. With flashers and park lights on do any lights operate correctly? I can't play your video. The ground terminal of socket contacts the metal side of bulb.

Did you do any work right before it started? Check your brake light switch above pedal and check your driving lights for dimming and also if you headlights are staying on slightly dim. My best guess is the wires to your lamps have a crimp in it near the headlamp motors, but I agree with ground issues. Very important did you do or have worked done before this happened ..any mods?

How hard was this car hit in the accident that caused you to be shopping door, bumper etc previously?

I checked the wires near the headlamp. No work done before this issue sprang up. No mods that would interfere with any of this. Going to check out the socket grounds next day it's a bit warmer. Figuring I can use a multimeter on them (?) to check for voltage when in various states

Not hard, was my fault, backed out of my garage with the door open a bit and it smashed up the door. I replaced it with an Ebay door from 93 but that door turned out to have been shoddily painted, seller lied about color.. so I put a third door on from a 96 (which was great since it was torch red and had matching internals, '93 internals were slightly different and didn't work out) and like a week later someone hit that new door and someone keyed the pass side. Really can't win with this money pit haha.. I'm probably going to dump the car even though it was my baby when I was 23 and got it, but I want to get it legal / inspected and running well before I try and sell it for cheap.

Also, thanks for the help everyone, this is been a hassle. I keep getting tickets (I'm in MA) for not having current state inspection since it is street parked and it costing me a ton, I don't have a garage / space anymore to park.

What happens when you use 'HAZZARDS'? That was asked earlier and I don't see where you mentioned anything! There's much going on that seems VERY ODD - VERY - VERY - ODD! The flashing DIC - C68 control and many others.

KEY ON/ENGINE OFF does the DIC display the expected? Do you have the FSM to use for diagnostics? I'd think many that have posted could maybe resolve if they had the car in their hands. The very short video just established the fact that there's 'much going on'!