Brake Light and Turn Signal Diagnostics

[Slemmy]

Hello! '65 LWB C10 w/230.

Had no brake lights, running lights, or turn signals. Can't remember if the dash indicators were lighting up. Bought a new turn signal switch at the recommendation of my mechanic and changed it out myself. Viola! Problem solved. All lights were working great for a couple of days. Until...

Now my in-dash signal indicators will sometimes blink, other times will stay on. No brake lights, running lights, or turn signal lights on the truck. Doesn't matter if my lights are on or not.

What are my diagnostic steps here? I'm fairly certain I can rule out the turn signal switch as I just replaced it with Echlin part # ECH DL6173.

Any help is appreciated!!

[Pssst]

Had a Very similar issue with my 66'. After replacing turn signal switch, headlight switch, AND dimmer switch, I turned my attention to the rear of the truck. Turned out the tail light housing did not have a good ground to the bed. I ran a separate ground wire from housing to the frame and BINGO! Lights have never been brighter and everything (tail lights, running lights, turn signals, etc) works perfectly. I have had other classic cars with electrical issues and bad grounds were the root cause. Kicked myself in the ass for not checking the grounds on my 66' FIRST before replacing parts

[Slemmy]

Thanks Psst!

Awesome advice! I've been doing some further research on here and the ground seems to always be the major culprit. I just dropped my head under the rear bumper to see if there were any ground straps from the rear lights to the frame, and I did not see any whatsoever. Any advice on wiring from the housing to the frame? I'll give it a go and see if that's not the issue.

[Pssst]

I wire wheeled the back of the housing, cleaned the contacts, wire wheeled where the housing contacted the bed, even added a 10g ground wire from frame to bed, and still didn't fix the problem. I finally used a small sheet metal screw and attached the terminal directly to the housing. make sure to put it low enough so you do not rip your fingers apart when replacing a bulb.

[Slemmy]

Complete with pics, too. Way to go! I'll give this a try and see what happens. Cheers!

[Pssst]

Originally Posted by Slemmy

Complete with pics, too. Way to go! I'll give this a try and see what happens. Cheers!

Thanks sir, just trying to help! Funny thing is, this issue came to light two weeks ago. Also, the "Screw IN Housing" is not the IDEAL way I'd like to have it, but with the 66' being my Daily Driver right now (in between leases), I could not afford to not drive the truck to and from work, lol.

[cwcarpenter98]

I spent a while trying to track down why my truck didn't have brake lights or running lights, but the blinkers worked just fine at the time. Took me almost six months due to high school and baseball, but once I did, I wished I had looked there to begin with. I ended up replacing the rear light harness that goes from the frame to the lights, but that still didn't fix my issue. Turns out it was the fuse block inside the cab. One day, my dad was messing with the back side of the fuse block and wiggling stuff around and sure enough everything started working. The contact points had gotten very rusty. It ended up making my wipers not work at all either. I bought a original style fuse block from Brother's, but the company who makes it is M&H Electrical Fabricators Inc.

http://www.wiringharness.com/

Hope that kinda long explanation helps

[Slemmy]

Originally Posted by Pssst

Thanks sir, just trying to help! Funny thing is, this issue came to light two weeks ago. Also, the "Screw IN Housing" is not the IDEAL way I'd like to have it, but with the 66' being my Daily Driver right now (in between leases), I could not afford to not drive the truck to and from work, lol.

I hear you. But until my girl gets the LS swap I’m cool with just getting her going on the road safely. She’s also living a bit of the work truck life hauling motorcycles, so for now this will do. Thanks again for your help. I’ll let you know how it goes.

OOC: Did either your blinkers or brake lights work before you found the ground issue, or was it all dark?

[Slemmy]

Originally Posted by cwcarpenter98

I spent a while trying to track down why my truck didn't have brake lights or running lights, but the blinkers worked just fine at the time. Took me almost six months due to high school and baseball, but once I did, I wished I had looked there to begin with. I ended up replacing the rear light harness that goes from the frame to the lights, but that still didn't fix my issue. Turns out it was the fuse block inside the cab. One day, my dad was messing with the back side of the fuse block and wiggling stuff around and sure enough everything started working. The contact points had gotten very rusty. It ended up making my wipers not work at all either. I bought a original style fuse block from Brother's, but the company who makes it is M&H Electrical Fabricators Inc.

http://www.wiringharness.com/

Hope that kinda long explanation helps

Hmmm. I hadn’t even thought to check there. I only checked the fuses. There is a long laundry list of culprits for this kind of thing. Glad to get feedback I hadn’t thought of from 2 people. I’ll check here also. Thanks for the link! I’m afraid that while I’m there I may buy a whole new wiring harness. Haha!

[cwcarpenter98]

Originally Posted by Slemmy

Hmmm. I hadn’t even thought to check there. I only checked the fuses. There is a long laundry list of culprits for this kind of thing. Glad to get feedback I hadn’t thought of from 2 people. I’ll check here also. Thanks for the link! I’m afraid that while I’m there I may buy a whole new wiring harness. Haha!

No problem at all. Unless the wiring harnesses throughout the truck is completely hacked up or destroyed, there is not necessarily a need for a whole new harness. The main reason I replaced the frame to taillight harness was because the PO had hacked it up pretty bad for some reason. Everything else was still good, and when I installed the new under dash harness that has the fuse block, everything went back to working right except the horn, but that's something inside the steering column. A project for another day

[Slemmy]

Pssst,

Thanks a million my friend. I wired the assembly straight to the frame and everything is working great now. Never been brighter actually!

Thanks a million for the advice and photo. Very helpful!

[jayoldschool]

I want to thank you guys for this thread. I remember cutting the cab to bed ground when I removed my bed, and never bothered to redo it. Last year, I started chasing an issue of a non-functioning left tail light. I tried everything, swapping bulbs, testing voltages, etc. No go. I bet it's a ground issue.