Electrical issues - lights

[Anthony Fremont]

66 GMC Custom long fender side. Everything was fine, but suddenly it's not.

What works:
headlights, bright indicator in dash, front park lights, front turns, REAR TURNS

What doesn't work:
dash lights, interior cab light, rear running/parking, brake lights

Still need to check all the fuses, but suspect it's in the headlight or turn signal switch after looking at wiring diagram. Anyone else experience these symptoms before?

EDIT: Is it even possible that only one fuse could be responsible for this much not working?

[63C20]

so, you posted before checking your fuses?

[Anthony Fremont]

Originally Posted by 63C20

so, you posted before checking your fuses?

Yes I did, but fuses should never blow unless there is a real problem (which there was). A blown fuse is a symptom and I was checking to see if someone else might have had the same issue before. The fuse could be replaced and things worked okay, until suddenly blowing again without warning. Honestly, I'm surprised that one fuse can take out so many things. Losing running and stop lamps together is kinda dangerous. I tried searching, but the search facility doesn't seem to limit itself to 60-66 trucks, so.....

Anyway, one of the locking tabs on the column sleeve had broken off allowing the whole assembly to rotate when I put it in park. This happened about a month ago, but didn't seem to be anything more than a nuisance. At first, I thought this might be the root of my trouble since so much wiring routes through there.

The actual root of the electrical problem seems to be inside the headlight switch. Apparently, sliding the stem out caused some kind of internal short resulting in the fuse being blown.

So now, I have two problems to deal with:
1) a broken tab on the column that seems like it is going to force me to replace the entire column to get the turn signal holder to stop rotating.
2) a bad headlight switch with some kind of intermittent short inside.

Installing a new headlight switch shouldn't be too difficult if I can figure out how to get the front bezel off. Taking the stem out was a piece of cake though.

Fixing the column seems to be pretty much impossible, unless I can find someone that can weld the little locking tab back on.

EDIT: I kinda felt dumb after reading your post, until I read some of your other posts. From now on, I won't.

[Brad54]

I had that exact thing happen. I ended up having two problems, but I think one caused the other.

The wires going to the Dimmer Switch burned. I don't know if the dimmer actually failed or not, but the wires were crispy.

The headlight switch was the original... the Bakelite housing has different metal contacts in it, that are essentially jumpers to complete different circuits. When you pull the knob out to the first stop, you have dash and running lights (including tail lights), when you pull it out one more, you have headlights. When you hit the dimmer switch, you have brights and regular lights.
I was driving along fat, dumb and happy one evening, when a VERY irate cop pulled up next to me and screamed to turn on my lights. Well, I thought I had!
No tail lights, but I had headlights.
And I had turn signals. So I turned on the right turn signal and drove with one "hazard" light working, so people could see the back of the truck.

I replaced the wiring (because the wires to the dimmer burned, and some others under the dash burned), I replaced the dimmer switch, and I replaced the headlight switch.
What I found with the headlight switch was that one of the contacts had fallen out of the Bakelight, and was free-floating inside the housing. I think it crossed the right (or wrong!) contacts, and shorted out, which burned up the wires.

I don't know if that helps you or not... Oh yeah, all this happened, and it never popped a fuse in the fuse panel.

-Brad

['63GENIII]

50 year old wiring can get like this. It seems like you have identified at least 2 problems so far. Start there, get them dialed in and move on to the next "unknown" issue (yes there are probably more). There have likely been previous owner / electrician modifications that come with varying degrees of quality and expertise.

It only took one small fire under the dash of the '63 for me to park it, pull every unnecessary wire out one by one until I was left with the original harness. I would stick to the factory size fuses instead of installing bigger ones (yes I've done that too), so that your wiring should be protected for the ampacity its rated at.

There are so many things that can make for an intermittent short that it can easily make a person crazy. I used to blow the tail light fuse when Id go around a corner hard and hit a bump. Seemed to happen at the same spot in town all the time. Turned out that the PO had wrapped the rear lighting harness around the frame but near one of the bed mounting points. Id go around a corner, hit the bump and that was all it took for the brake light wire to get in between the rubber pad for the bed mount and the frame. Poof. Every time. Took a few months to figure it out. Took 10 minutes to trace that harness from the firewall connector all the way back to the tail lights and find the smallest break in the insulation. A little scotch 33, some scotch kote splice sealer, a few tie wraps to secure the harness to the frame and its been trouble free for 7 years. It also made me tighten up the bed mounting bolts.

Stick with it. Its a pain in the shorts to find the shorts but with some patience and a keen eye, you'll get it.

['63GENIII]

EDIT: Is it even possible that only one fuse could be responsible for this much not working?[/QUOTE]

Anything is possible. IIRC, mine has separate tail and dash fuses.

One other consideration to think about. When these trucks were built, there weren't a whole lot of accessories to power. Im not sure if you have any extra lighting, stereo or anything else. If not, should be easier to "thin out" any extra wiring if you have any. If you do have any extra stuff, you might want to disconnect it until you have the rest sorted.

Lets hope that the column and headlight switch do the trick. Good luck!

[Anthony Fremont]

Thanks guys, I appreciate the input. Two of the wires going to turn signal switch assembly had small nicks in them. I really couldn't see anywhere that they might be grounding out, but with the whole thing rotating on the column and given some of the sharp edges in there, it's a possibility that they were shorting to ground.

With all of that unplugged, I found that the headlight switch was also causing the fuse to blow when pulling it out. Definitely something wrong in the headlight switch. I never liked the idea of routing all that headlight power (unfused) through the dash switch. I can't imagine why the factory didn't use a relay in the style of the aftermarket harnesses that are available. I wonder how many dash fires have occurred because of this.

In the long run, I plan to replace/upgrade the entire harness with an aftermarket setup that has more fuses and capacity. The only add-on accessories that I currently have are some gauges (tach, voltage, oil-pressure and temp (mechanical). I also have an electric fan. I do want to install a stereo and amp later, but I'll need to upgrade the alternator before I do that.

Amazingly, my harness hadn't been hacked up by POs. I did have to replace the front parking light piece and the section running from the cab to tail lights because of general decay from 50 years of Texas weather.

As for my other mods, I added a relay to the starter solenoid to take some work off the original ignition switch. Instead of carrying all the current to activate the starter solenoid, it now only has to carry enough current to switch a relay added near the starter. This cured the hot-no-start problem that so many older vehicles seem to have.

The electric radiator fan has a relay as well and heavy wiring added that runs directly to the battery. I'm using a battery that has top and side posts. I use the side posts to power an addon distribution fuse box (for the fan and HEI distributor). I added that to avoid adding any additional load or modifications to the factory harness. I'm powering the added gauges from the little tabs on the factory fuse box. IOW, I didn't hack up the factory setup in any way. Everything I've added is easily reversible.

After on scary event about 35 years ago with some unfused wiring for an aftermarket 8-track player, I've become a big fan of fuses. My next mod will be to convert the headlight circuit to a relay/breaker setup. The benefit being not only a safer amount of current through the switch, but brighter headlamps.

How do I get the factory headlight switch out? I know how to get the stem out, but don't know how to get the front bezel off.

['63GENIII]

I believe that the HL switch bezel should spin off if it's the same as a 63. You already got the stem out which was the biggest battle for me until I was informed about the button on the back side of the switch. My bezel was pretty tight IIRC.

The headlight relays are an upgrade you will not regret. Did mine a few years back an now it seems like a modern day vehicle with modern lighting. Definitely worth it.

Going with a new fuse box myself for added space and less clutter under the dash. Have one from the 97 c3500 that I got my engine from. It has a #2 feed from the battery and lots of factory relays in it. Should be able to get my horn, lights , fuel pump and still have room to spare.

Let us know how yours goes.
Good luck!

[Anthony Fremont]

Thanks, I didn't want to tear it up trying to spin it off. Engineers sometimes come up with some really interesting ways to handle things like that. I do some amateur vintage watch repair at times and figuring out how to open a case can really be a challenge. Must be dozens of things that they've come up with for that.

In the long run, I want to convert my intake to a TPI system and swap that powerglide for a four speed automatic. That's really going to be an interesting process, but way down the road. Once I got my truck driveable, it really slowed down the progress of my plans. It really is the poster child for the old adage about eating an elephant.

I was fortunate to get a fairly unmodified survivor (outside of the V6 being long gone), but after spending 20 years in the South Texas pine forest, it really needed a LOT of work. I didn't have to take a lot apart, since someone had already started that. The bed was literally filled with all the pieces. But for four or five hundred bucks, I think I got a good deal. Only about two or three hundred hours of head scratching and cussing to get it back on the road.

[oliver63]

Lack of a good ground is the cause of a lot of problems...

[Brad54]

I installed an American Autowire Harness kit in my '61 Suburban, and my '57 Chevy.
It's a fantastic kit, easy to install, every wire is clearly marked the whole length of the wire (making life a hell of a lot easier!), and their instructions are fantastic.
Not only do the pictures show the harness being installed specifically on one of our trucks (a rarity in the aftermarket industry), but the instructions covered the specifics for each of our instrument clusters, including '60-'63 idiot lights only, '60-'63 full instrumentation, and the same for '64-'66.

My one criticism is that it uses plastic snap-on dash light sockets, and they don't stay in. I've pirated several dash harnesses since, to use the factory metal sockets. I'll re-do the one in the Suburban at some point, and will use them on the K10 project I've got lined up.

-Brad

[aggie91]

To take out the bezel for the light switch, I used a pair of needle nose pliers as a make shift spanner wrench. Each point of the pliers in the slot on each side of the bezel. I used an adjustable wrench to grab the pivot part of the needle nose and used one hand to push down on the needle nose and the other to rotate it with the adjustable wrench.

to answer one of the OP's original questions, YES, one fuse could cause all your lights you listed to go out. There are 2 fuses that feed power thru the light switch. One of them is the main key feed to the switch that also feeds the dome light. Sounds like you figured out the main issue is your headlight switch.

['63GENIII]

Originally Posted by oliver63

Lack of a good ground is the cause of a lot of problems...

Very important point there. When doing the FI on the '63, I noticed that there were no grounds except for the one from the negative cable to the core support and where the negative cable terminated on the frame. Ended up buying an assortment of braided ground straps from Summit in order to ground the cab to frame, bed to frame, and a big ol' one from the engine to frame. I think it does help make a clean path to ground avoiding the possibility of voltage "seeking" a way through less desirable paths .