Headlight Grounding

[cmroles]

Well...



I solved one big problem today. Thanks to all the info I found by searching this site I tracked down a broken ground wire at the Passenger Side headlight connector and successfully replaced it.

For anyone else who may have a similar problem, here are the symptoms I had:

1. Passenger-side headlight functions but very dimly
2. When headlights were ON the right turn-signal indicator on the dash would be faintly illuminated
3. When the right turn-signal was actually operating the headlight would blink with the signal....

After inspecting the wiring I also found that the 10ga ground wire between the Body and Chassis was in really bad shape. The insulation had fallen off (see pic) and the wire was fairly corroded. I built a new harness using some watertight ring-terminals and some 10ga and 14ga wire. I also cleaned up the ground spots on the chassis and body and applied some dialectric grease to keep them from getting rusty.

Now: The remaining "turn-signal" problem I have is that the Left signal illuminates whenever the brake pedal is pressed. The signals all work as they should (front / rear blink when signal engaged), but whenever I hit the brakes the left ones lite up. I've been through the wiring diagrams and I'm not seeing any common point between brake-light circuits and turn signals. Is there something I'm missing?

 

[mistaken1]

Good work tracking down that elusive (missing) ground.

Doesn't the brake light circuit and turn signal circuit energize the same filament in the tail lamps?

 

[cmroles]

Good work tracking down that elusive (missing) ground.

Doesn't the brake light circuit and turn signal circuit energize the same filament in the tail lamps?

I haven't looked to see if they do or not.

Has anyone had experience with this type of problem before? I am going to be replacing the turn-signal / wiper switch since the dimmer portion is pretty sketchy. Hopefully replacing that switch will correct the issue with the driver side turn-signal as well...

 

[Capt.Marion]

Are you replacing the lever, or the actual dimmer switch that is mounted on the steering column and is actuated by a rod connected to the lever?

 

[Oldsouthernboy]

go check the the light bulbs themself's, if the bulb it self is defective, glass loose or broken from the base it can still work but cross feed. The best bet is to replace all the left side light bulbs, take a pencil and clean the inside of the sockets, both the base contacts and the side ground. on the rear clean the ground bolt under the light assy . You will have to remove the tailght unit base it self.

 

[Whit]

Where exacthly is the ground wire between the "body and the chassis". My headlight fuses keep blowing, and the ground on the inside near the fusebox seems to be OK. Sounds like there is yet another ground I need to check. Thanks

Whit

 

[cmroles]

Where exacthly is the ground wire between the "body and the chassis". My headlight fuses keep blowing, and the ground on the inside near the fusebox seems to be OK. Sounds like there is yet another ground I need to check. Thanks

Whit

The ground wire that you are looking for is inside the engine-bay on the passenger side of the vehicle.

You will see a ground-wire with ring-terminal attached to (I think) the radiator support right in front of the front battery. I actually had to move the battery hold-down plate to the the bolt out.

From this ring-terminal there is a ground wire that goes down top of the passenger side frame rail. There is a second wire that splits off to the passenger side headlight connector. If this ground is not there the headlights will behave very strangely...

 

[Whit]

Thanks:

I actually found that one yesterday before the big snowstorm hit here in Atlanta, and filed it up so the contacts on both wires would be good. Did not know what the second wire was, though, so I will trace that one backward to the other headlight. Thanks for the tip.

Whit

 

[Warthog]

This even happens on Civvy vehicles.

I picked up the Dept on Interior Suburban from Vegas last friday. The head lights where not functioning correctly. Same symptoms as CMROLES but on the drivers side.

Parklights functioned correctly, side markers working, but when you turned on the headlights, the passenger side low beams worked but the drivers side low beam and both high beams would come on dim. Also the drivers parklights dimed along with the sidemarker. And the drivers side turn signal indicator on the dash would glow.

Popped the hood and checked the ground wire. There it was just sitting there.

A few minutes removing the bolt, cleaning the mounting surface and bolt, and then installing a new ring terminal.

Hit the lights and everything is working as it should.

SO CHECK AND CLEAN YOUR GROUND WIRES!!!

 

[cmroles]

Thank to everyone for their suggestions so far, but unfortunately this one is not wrapped up yet.

So far what I have done:

1. Checked grounds at taillights (used a dremel with grinding wheel to take off some paint and clean up the ring terminal)

2. Checked wiring at taillights (no breaks or obvious problems)

3. Traced out and checked wiring at front turn-signals / marker lights and didn't find anything weird.

4. Checked headlight grounds and they look OK.

For some reason, when the brake-light switch activates, power is being supplied to the driver-side turn signals as well as the brake light. The signal doesn't flash, just comes on steady as long as the brake is held down.

Any other thoughts are appreciated!

 

[MakersTeleMark]

Thank to everyone for their suggestions so far, but unfortunately this one is not wrapped up yet.

So far what I have done:

1. Checked grounds at taillights (used a dremel with grinding wheel to take off some paint and clean up the ring terminal)

2. Checked wiring at taillights (no breaks or obvious problems)

3. Traced out and checked wiring at front turn-signals / marker lights and didn't find anything weird.

4. Checked headlight grounds and they look OK.

For some reason, when the brake-light switch activates, power is being supplied to the driver-side turn signals as well as the brake light. The signal doesn't flash, just comes on steady as long as the brake is held down.

Any other thoughts are appreciated!

Sounds like your hazard light switch is funky.

 

[Warthog]

Have you checked/cleaned the ground wire above the parking brake?

This ground supplies many circuits. It can be mount anywhere in the general area.

Also double check the underhood ground for the left side lights.

Looking at the diagrams, the stop light circuit travels thru the turn signal/hazard switch on the column. It may be a dirty switch.

 

[cmroles]

Have you checked/cleaned the ground wire above the parking brake?

This ground supplies many circuits. It can be mount anywhere in the general area.

Also double check the underhood ground for the left side lights.

Looking at the diagrams, the stop light circuit travels thru the turn signal/hazard switch on the column. It may be a dirty switch.

Thanks. I'll double-check the headlight grounds. The ground underneath the dash looks clean and undamaged.

As for the hazard switch....I hadn't thought of that. I may just replace that switch on general principle...

 

[grw800]

The rear turn signals and brake lights are one and the same: the same filament in each rear bulb serves as both the turn signal and brake light. So I think you mean that the front driver side turn signal and indicator are lighting when you step on the brake. The turn signal switch also acts as a brake light switch--when you activate a turn signal, the switch opens the circuit to the brake light on that side. If it didn't do this, the turn signals on both sides would flash together. Also the brake light would stay on and you wouldn't see the turn signal flashing. Look at the schematic and you'll see that the brake light circuit passes through the turn signal switch. So I would guess that your problem is in the turn signal switch itself. Have you tried wiggling the switch lever when you step on the brake?

 

[cmroles]

The rear turn signals and brake lights are one and the same: the same filament in each rear bulb serves as both the turn signal and brake light. So I think you mean that the front driver side turn signal and indicator are lighting when you step on the brake. The turn signal switch also acts as a brake light switch--when you activate a turn signal, the switch opens the circuit to the brake light on that side. If it didn't do this, the turn signals on both sides would flash together. Also the brake light would stay on and you wouldn't see the turn signal flashing. Look at the schematic and you'll see that the brake light circuit passes through the turn signal switch. So I would guess that your problem is in the turn signal switch itself. Have you tried wiggling the switch lever when you step on the brake?

I just went and goofed around with it to verify exactly what is happening. The problem is isolated to the front driver-side indicator light.

1. Turn the headlights on the parking-light filament illuminates normally.

2. Turn the left turn-signal on the turn-signal filament blinks as it should

3. Step on the brake pedal the left turn-signal filament illuminates steadily (parking light filament stays on as it should)

4. Put on left turn-signal WHILE stepping on brake and turn-signal filament begins to flash properly.

The issue seems to only actually present itself when stepping on the brakes with the left turn-signal OFF. When this happens the left turn-signal filament illuminates steadily. If the signal is already on and I step on the brakes there isn't anything strange happening. The right turn-signal has no affect on this situation at all. Since I fixed the headlight ground to the passenger side it works exactly as it should.

I also pulled out both the hazard and turn-signal flashers to see if it still comes on with the brakes and it does.


It seems that if I hold the brake pedal and push the turn-signal lever down (but not all the way to where it clicks) the front-left light will go out. I'm thinking that grw800 may be correct in thinking that the turn-signal switch itself is bad. The lever is definitely a little floppy. There is quite a bit of play in the lever and it can wiggle around a fair bit. Guess I have to pull the steering wheel after all....

 

[cmroles]

Well....the Turn Signal / Hazard switch is now brand-spanking-new and the problem still exists.

As it is everything works perfectly normal with one exception: If I press the brake pedal the front driver-side turn-signal will come on steadily. If I put on the turn signal while holding the brake pedal down it will start blinking normally.

I've been through the wiring harness for the lighting up front without finding anything wrong. Now the turn-signal / hazard switch has been replaced with no results.

Any thoughts?

 

[grw800]

Take a good look at your left rear taillight/turn signal/brake light socket and bulb. Make sure there is no short there between the taillight terminal and the turn signal/brake light terminal of the socket. Also look at your left front side marker light socket and bulb.
Here's what I am thinking: Circuit 18 is the left rear turn signal/brake light, and feeds one terminal of the rear taillight/left turn signal/brake light socket. The other terminal of this socket is Circuit 9, taillights/marker lights. Maybe there is a short there, and Circuit 18 is backfeeding Circuit 9 at that socket. Circuit 9 and Circuit 14 meet at the left front side marker light bulb. Guess what circuit 14 is? The left front turn signal!
The left front side marker light is an interesting animal. Look at the schematic and you'll see that it has no ground. One pin of the bulb is fed by Circuit 9, the taillight/ marker light circuit. The other pin of this bulb connects to Circuit 14, the left front turn signal (and indicator). When the taillights/marker lights are not on, the left front turn signal and left front side marker light flash simultaneously. When the taillights/ marker lights are on, the left front turn signal and left front side marker light flash alternately. This is because the left front side marker light is grounded through the filament of the left front turn signal bulb. When the left front turn signal bulb illuminates, it breaks the ground of the left front side marker light bulb and causes it to go off, thus flashing alternately with the left front turn signal.
Confused? I am! But this just might somehow be the key to your problem. Look at the bulbs and holders I mentioned, and see how things work with no bulbs or different bulbs in these places.

 

[Warthog]

So what was the outcome of this problem?

 

[cmroles]

So what was the outcome of this problem?

Sorry for being so late posting this resolution.

Basically, some nimrod had installed a wire splicer between the left taillight wire and the left-front turn signal wire.

My guess is that the turn-signal switch failed and the front-left no longer functioned. Rather than pull the wheel and replace the switch they just jumped taillight power to it for a "temporary" solution....

The splice was made right at the firewall connector with the type pictured below. It was sort of buried in the wires and I didn't notice it until about my 5th time picking through all the wiring looking for shorts. I pulled off the splicer and problem solved.

As part of the troubleshooting I had replaced the original turn-signal switch, so I'm unable to verify my theory regarding why this was done, but its the only thing that makes sense...

 

[Warthog]

Thanks for the followup. We would have never guessed the jumper wire. Good find.