brake lights and dash lights don't work anymore.

[BigMike56-72]

I know there are lots of post about issues like this but I still cant figure out what is going on here (I've read many post and it always seems to be a ground issue, maybe the same for me but I can't find it). Up until a few days ago everything was working fine but now I have no dash or brake lights. The headlights work and my turn signals also work. I really suck at troubleshooting electrical issues. I checked my fuse panel and all the fuses look like they are good to go. None of them were popped. I decided to put a test light on each fuse to see if they were all getting power and noticed that all but one was getting any power. (The fuse PNL LTS" has no power what so ever) I tried to trace down where this wire supposed to get it power from couldn't find the source power. I am pretty sure this fuse should be getting power from somewhere and hoping thats why my dash and brake lights stopped working. For now I am stuck and I am hoping one of you can help me along here. Until then my truck sits parked in the driveway.

Mike

[LockDoc]

-
Hook a jumper wire from the CIG terminal (should be hot all the time) to the PNL LTS fuse and see if the lights work then. Preferably a wire with alligator clips or proper wire terminals on it.....

If the lights work I would suspect the HL switch.

LockDoc

[NoNeck]

Hook a jumper wire from the CIG terminal (should be hot all the time) to the PNL LTS fuse and see if the lights work then. Preferably a wire with alligator clips or proper wire terminals on it.....

If the lights work I would suspect the HL switch.

What Doc said.

POP

[BigMike56-72]

I will try that now and see what happens. I will report back with my findings.

Thanks

Mike

[BigMike56-72]

Originally Posted by LockDoc

-
Hook a jumper wire from the CIG terminal (should be hot all the time) to the PNL LTS fuse and see if the lights work then. Preferably a wire with alligator clips or proper wire terminals on it.....

If the lights work I would suspect the HL switch.

LockDoc

LockDoc

I tried what you said and my dash lights and brake lights work when I crossed connected the fuses. So would you say my 1st thing to replace would be the HL switch like you mentioned?

Mike

[VetteVet]

The headlight switch is powered from two sources, A large red wire from the constant hot battery alternator junction, and an orange wire from the fuse panel
which is also constant hot. This orange wire also powers the exterior parking and marker lights.

The dash indicator lights are powered by the orange wire through the headlight rheostat (dimmer) and a green wire back to the fuse panel Pnl Lts fuse.

The Pnl Lts fuse connects the green wire with a gray wire to the instrument cluster. By jumping the fuse you bypass the headlight switch and the green wire so you determine that the problem is the connection in the orange/rheostat or the rheostat/green wire or in an open in the green wire to the fuse panel.

My best guess is the rheostat in the HL switch has lost connection in it's circuitry.Several rotations of the knob may restore that or not. If not then I agree with the Doc and NoNeck and you will have to replace the HL switch.





Heres the diagram of the headlight switch wiring




Here is the fuse panel diagram of the panel lights. Notice the green wire to the PL fuse.

[Rufas]

Just for grins try replacing the fuse. Just because it 'looks ok' doesn't mean voltage will pass through it. Even checking the resistance might not be a good check. That fuse could be 40+ years old.

[LockDoc]

Originally Posted by Rufas

Just for grins try replacing the fuse. Just because it 'looks ok' doesn't mean voltage will pass through it. Even checking the resistance might not be a good check. That fuse could be 40+ years old.

I may have misunderstood but I think he tested both ends of the PNL LTS fuse with no power on either end. If that is the case then replacing the fuse won't make any difference.

LockDoc

[VetteVet]

That's the way I took it too Doc. course it wouldn't hurt to replace the fuse and clean up the terminals.

What say you Big Mike?

[BigMike56-72]

Thanks for all the help on this guys. I replaced the fuse just for the hell of it and still nothing. Like Doc said I don't even get power to that fuse anymore. I also replaced the headlight switch and it still doesn't work.

If I have no power at the fuse and have replaced the HL switch what should I do next? I mean s**t, it was working fine on Friday and now this truck wants to stress me out with electrical bug issues. LOL.

Mike

[BigMike56-72]

I also replaced both battery cables and cleaned up the little wire mess the truck had when I got it. I also removed the ground connections under the hood and sanded down to metal so I would have good ground. I also looked for cracked/broken wires/touching wires and nothing.

Again the head lights work. My rear lights (flash) work when I turn on the turn signals but no dash lights and or parking/brake lights.

[VetteVet]

Originally Posted by BigMike56-72

I also replaced both battery cables and cleaned up the little wire mess the truck had when I got it. I also removed the ground connections under the hood and sanded down to metal so I would have good ground. I also looked for cracked/broken wires/touching wires and nothing.

Again the head lights work. My rear lights (flash) work when I turn on the turn signals but no dash lights and or parking/brake lights.

Here's the clue.
but no dash lights and or parking/brake lights.

In my post I said that the orange wire to the headlights powered the parking and the dash lights.

You never said that you had no parking lights or any brake lights.

the orange wire also powers the brake lights and the dome light. It runs to the headlight switch, the stoplight switch and to the dome switch connector.
Study the last diagram I posted and you can follow the orange wire from the fuse panel to those switches. The orange wire is a constant hot wire fed by a red wire from a junction in the harness. You have probably lost the connection on the large red wire to the fuse panel.

Check for power on the stop tail fuse and the dome light fuse.
If they are good then you can troubleshoot the orange wire circuit by jumping from the Cig terminal to each of those fuses like you did with the PNL LTSS fuse.\

In fact you must have power to the fuse panel on the red wire or the first check you did would not have worked. I suspect that you may have a bad connection on the back of the fuse panel where the red wire comes in.

The turn signals have no bearing on your problem, they are on a completely different circuit, however the hazards are on the orange wire circuit, so check them to see if they work.

Look at the fuse panel in the bottom right of the diagram and see the red power wire that comes in to power the orange wires. Then trace the orange wires and you'll see how they power the switches.

[LockDoc]

Originally Posted by VetteVet

Here's the clue.
but no dash lights and or parking/brake lights.

In my post I said that the orange wire to the headlights powered the parking and the dash lights.

You never said that you had no parking lights or any brake lights.

the orange wire also powers the brake lights and the dome light. It runs to the headlight switch, the stoplight switch and to the dome switch connector.
Study the last diagram I posted and you can follow the orange wire from the fuse panel to those switches. The orange wire is a constant hot wire fed by a red wire from a junction in the harness. You have probably lost the connection on the large red wire to the fuse panel.

Check for power on the stop tail fuse and the dome light fuse.
If they are good then you can troubleshoot the orange wire circuit by jumping from the Cig terminal to each of those fuses like you did with the PNL LTSS fuse.\

In fact you must have power to the fuse panel on the red wire or the first check you did would not have worked. I suspect that you may have a bad connection on the back of the fuse panel where the red wire comes in.

The turn signals have no bearing on your problem, they are on a completely different circuit, however the hazards are on the orange wire circuit, so check them to see if they work.

Look at the fuse panel in the bottom right of the diagram and see the red power wire that comes in to power the orange wires. Then trace the orange wires and you'll see how they power the switches.

He mentioned that he didn't have any dash lights or brake lights in his first post, second sentence, but he said they worked when he run the jumper wire from the CIG terminal to the PNL LTS.

LockDoc

[chainsawman]

I had the same problem on my 68. Drove me nuts for 2 days.Turns out it was rust on the fuse holder tabs. Scaped and sanded them, and that solved my problem.

[BigMike56-72]

LockDoc and VetteVet just wanted to give you both a big thank you. I still have not solved my issue but I really appreciate you guys trying to help me out here. Once I do figure this out I will be sure to post the fix so that if anyone else runs into this they will know what to look for. Man this is killing me! I spend all day trying to figure out what is wrong and I'm still stumped.

Mike

[BigMike56-72]

Originally Posted by chainsawman

I had the same problem on my 68. Drove me nuts for 2 days.Turns out it was rust on the fuse holder tabs. Scaped and sanded them, and that solved my problem.

Thank you. I am going to try that tomorrow after work. Hopefully it's a easy as that. Man what a pain in the rear this has become. LOL.

[VetteVet]

Originally Posted by LockDoc

He mentioned that he didn't have any dash lights or brake lights in his first post, second sentence, but he said they worked when he run the jumper wire from the CIG terminal to the PNL LTS.

LockDoc

Yeah I saw that after I posted, I was concentrating on the parking lights and the headlight switch and the dash lights all at the same spot, which are fed by the orange wire there. The brake lights are fed off the same circuit but I didn't register that when I red his post. I did cover it though and I'm pretty sure the problem is in the fuse panel.

[BigMike56-72]

No update as the weather has been bad here the last few days. I am hoping I can get this resolved soon so I can drive my truck again.

[LockDoc]

Originally Posted by BigMike56-72

No update as the weather has been bad here the last few days. I am hoping I can get this resolved soon so I can drive my truck again.

Looks really bad out there. I hope you are not in the middle of all that.

Keep us updated when you get the chance.....

LockDoc

[BigMike56-72]

Well I finally had some time to work on this issue and I am glad to say it is fixed now. My guess is that it was a bad fuse. Not the PNL LTS fuse because I had already replaced it. I went one by one with a test light and was touching the top and bottom of each fuse. I noticed that on one of the fuses TAIL STOP I had power on the bottom connector and not the top. The fuse was not popped so I said what the hell and removed it. In doing so the metal cap came off very easy. I was like hum.. that's not good so I replaced it with a new fuse and boom my PNL LTS fuse that wasn't getting any power started to work. I don't know why or if it's supposed to work like this but hey I'll take it. I can now drive my truck again. YES!!! I guess the moral of the story is to check your fuses in detail because even though they don't looked popped they can still be bad. Thank you to everyone who helped me out here.

Mike

[LockDoc]

Originally Posted by BigMike56-72

Well I finally had some time to work on this issue and I am glad to say it is fixed now. My guess is that it was a bad fuse. Not the PNL LTS fuse because I had already replaced it. I went one by one with a test light and was touching the top and bottom of each fuse. I noticed that on one of the fuses TAIL STOP I had power on the bottom connector and not the top. The fuse was not popped so I said what the hell and removed it. In doing so the metal cap came off very easy. I was like hum.. that's not good so I replaced it with a new fuse and boom my PNL LTS fuse that wasn't getting any power started to work. I don't know why or if it's supposed to work like this but hey I'll take it. I can now drive my truck again. YES!!! I guess the moral of the story is to check your fuses in detail because even though they don't looked popped they can still be bad. Thank you to everyone who helped me out here.

Mike

Glad you figured it out. Electrical gremlins can be frustrating for sure....

LockDoc