Not the normal brake light issues.

[FormerBMWOwner93]

so after searching around here and google, I’ve come up short on answers.

I don’t have brake lights in the normal sense. My rear brake lights stay on(hundred threads on here for that, read them all) but in my case, they only stay on with the ignition on. Pretty reasonable to assume it’s an ignition related issue right? Well ignition switch has been replaced three times now. No luck.
Let’s see..
I’ve also replaced, brake lamp relay, all related fuses, bulbs, circuit boards in the tail lights, brake pedal switch, multifunction switch, neutral safety switch(unrelated issue, but was replaced recently) I’ve cleaned and tighted all grounds that I could locate.

My turn signals work fine, my hazards stay solid when on.

Could it be the flasher under the dash, even with the turn signals working? Broken wire? Truck is possessed and needs exorcism?

My knowledge on electrical work is extremely basic.

My third brake light has never worked at all since owning the truck. Neither has the cargo lights. I know this is a different circuit, but worth mentioning.

Someone please guide me to getting one or all the lights working. Using hand signals while driving is a PITA!

 

[Jay33089]

Being as they are only on with the ignition on, and they go solid with hazards. I'd say the brake switch and circuit is working correctly. I would look at the hazard switch or turn signal switch. (I read that you have replaced both) keep looking at the harness, maybe chaffed wires. Do the brake lights and hazards work correctly with the ignition off? What year truck is it?

 

[FormerBMWOwner93]

Being as they are only on with the ignition on, and they go solid with hazards. I'd say the brake switch and circuit is working correctly. I would look at the hazard switch or turn signal switch. (I read that you have replaced both) keep looking at the harness, maybe chaffed wires. Do the brake lights and hazards work correctly with the ignition off? What year truck is it?

The truck is a 1996 C1500 Silverado.
The brakes/hazards don’t work at all with the truck shut off.

 

[Jay33089]

Has the steering column been replaced? It almost sounds as if wires are crossed up in the big connector for the column. I have to say your right! Not the normal issues at play here. Is this something that just started happening or after something was replaced? Or did the previous owner fail to tell you about it. Your brake lights and hazards should work all the time even with the ignition off. This is why I say something is crossed. I wish I could be more help. Without being there with a voltmeter and test light all I can do is speculate. I wonder if you have any parts out of a 95 in there? If I'm not mistaken a 95 has a lot of one year only electrical parts. As it has the newer dash with the TBI engine.

 

[MechMike]

So I’m having the same issue on my 93. Noticed the lt grn wire from the taillights is fried all the way to some sort of junction box on the fire wall below the hydro booster. I’m still investigating but at a loss as if now

 

[FormerBMWOwner93]

So I’m having the same issue on my 93. Noticed the lt grn wire from the taillights is fried all the way to some sort of junction box on the fire wall below the hydro booster. I’m still investigating but at a loss as if now

But you still have power and ground at the connector that plugs into the lights??
I can’t seem to find any broken wire, nothing looks melted, and I’ve compared all my wiring to three different trucks at the scrap yard. Everything matches up.

 

[FormerBMWOwner93]

Sorry I haven’t replied to anyone in a while, working two jobs has made tearing into the truck difficult.

I have zero knowledge on electrical stuff, but If I’m understanding correctly, the brake lights are always hot. And when they get ground, they light up? Since mine are constantly lit, there would be something grounding out, right?
Or do I have that backwards?
I have power(confirmed via multimeter/test light) at the plug in the tail lights.

I’m starting to think it could be the ground wire running from the brake light switch at the pedal since that’s the next ground wire I could locate in the circuit working backwards from the lights. Does anyone know which wire it is, and where it runs to? Did I miss another grounding point between those two?

I have a feeling I’m gonna have to go bumper to bumper cleaning and replacing ground wires. While changing the oil a few days ago, I found a homemade ground wire running from the back of the block to the wheel well. It was burned up pretty bad. If the truck had grounding issues before I bought it, it’s possible that all that electricity fed through other grounds and cooked them as well,such as my lights.

 

[delta_p]

The truck is a 1996 C1500 Silverado.
The brakes/hazards don’t work at all with the truck shut off.

If this is a 1996 C1500 the brake lights and the hazards should work with the key off and out. This is because the only thing that is in "hot in run or start" is the fuse feed to the turn/hazard relay when the hazard switch is in the off position. Everything else to switches etc. is in "hot at all times". With the hazard switch on the feed to the relay is now from "hot at all times". The feed to the brake switch is from "Hot at all times".

 

[delta_p]

Sorry I haven’t replied to anyone in a while, working two jobs has made tearing into the truck difficult.

I have zero knowledge on electrical stuff, but If I’m understanding correctly, the brake lights are always hot. And when they get ground, they light up? Since mine are constantly lit, there would be something grounding out, right?
Or do I have that backwards?
I have power(confirmed via multimeter/test light) at the plug in the tail lights.

I’m starting to think it could be the ground wire running from the brake light switch at the pedal since that’s the next ground wire I could locate in the circuit working backwards from the lights. Does anyone know which wire it is, and where it runs to? Did I miss another grounding point between those two?

I have a feeling I’m gonna have to go bumper to bumper cleaning and replacing ground wires. While changing the oil a few days ago, I found a homemade ground wire running from the back of the block to the wheel well. It was burned up pretty bad. If the truck had grounding issues before I bought it, it’s possible that all that electricity fed through other grounds and cooked them as well,such as my lights.

The lights are connected to ground. The voltage feed to them is from the hazrd/turn switch to the lights. The only brake lights that are not through the hazard/turn switch is the third brake light, directly off the brake light switch.

 

[delta_p]

I wanted to post this sketch of the turn/hazard switch i made after seeing a schematic. I believe it to be accurate for my 1996. The dashed lines mean all the contact bars move up or down together for the hazard, or all the contacts rotate together for the turn signals.

The brake lights on the truck flash on/off for hazard or one blinks on/off with the other burn steady like if are stopped in a turn lane with brake engaged and blinker on.

You can see why the blinkers don't work unless the key is on, you can see why the brake lights and hazards work without the key in, you can see why when the hazards are on and you depress the brakes, the lights quit flashing and burn steady, you can see how the rear light opposite the turn signal light is made to burn steady with brakes depressed.

But the biggest thing you can see is how one of the weakest switches in the truck (the hazard switch) can shut down operation of the tail light system

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