I got my truck to the point where it can run again, but naturally the wiring for the brakes isn't working. I'm slowly isolating the issue. It seems that there's a sink somewhere in the system before power gets to the flasher or the brake switch (I just replaced both of those). After I replaced the flasher I had a huge jump in voltage going through that, which I figured was a good sign. Cycled the accessory switch again and all of a sudden I've only got 1V passing through the flasher instead of the 11V I had when I first replaced it. Figure I think need to look closer to the battery in the system, so the next steps are the ammeter, fuse box, ignition switch itself, and junction box. Anyone have suggestions on where to look? I'm going through and trying to clean all the connections and make sure the grounds are solid. Am I just ignorant and forgetting how the electrical system is supposed to work? I've hardly worked on electrical systems before so I'm just feeling my way through this.

 

What doesn't work, and what does?

Eric

 

Right, that's probably important information. The left turn signal works, right one barely lights up, brake lights don't work.

 

Also thinking it might be the turn signal switch

 

Got everything to work for a few minutes by messing with the turn signal switch, but after taking it out on the road and bouncing around quite a bit I've once again lost power to the lights. The now I'm not getting any power to the flasher, so I have to be losing power somewhere before that.

 

If you have had too much apart yet, you will. Old connections get "old"! Grounds get loose and corroded while previously owners can set you up for failure. Do you have a decent wiring diagram? Here's a pic of an overall one for a '67, might be close.

https://www.the12volt.com/installbay....asp?tid=56100

do you have a shop manual yet, worth it's weight in gold! Master parts catalog is awesome as well. They can be bought in old paper form or digital.

 

Just as Spurredon said previous owners don't have a clue, and start cutting and splicing wires and setting you up for failure. I've owned a bunch of those projects and had to straighten out a rats nest. You need to inspect your wire loom, take all the electrical tape off and inspect all the connections and wires.(electrical tape where the P.O has made splices) Do you get power back when you move any of the wires or loom? Check your grounds on lights, check for the cab grounds, check the frame grounds, engine grounds, everything. All these mentioned have to be grounded correctly before will have any success. It sounds like you have a loose connection some where. Or could be an electrical component. It's frustrating but keep with it you'll find it. Have you taken the light switch out of the dash to check your connections? Check your wires coming out the steering column for your signals. And as stated get a manual with wiring diagrams

 

I found a couple wiring diagrams online, printed them out, and have been out there making sense of where everything goes. I found out the PO had thrown some tinfoil and other random garbage in the fuse box rather than using fuses, so that definitely contributed to the issue. Still trying to find where all the grounds are located to make sure they're solid.

http://www.fordification.info/tech/images/wiring/1966fordtruck_masterwiring.jpg
http://www.fordification.info/tech/images/wiring/66extlight2s.jpg

A while back I did pick up a set of the shop manuals. Haven't found the wiring diagrams in them though, maybe I just haven't looked hard enough.

 

Just looked all over the truck and the only main ground I can find is between the battery and block. Can't see any ground straps between block/firewall, cab/frame, or bed/frame. Tomorrow I'll go pick up some straps and get that sorted out. Any suggestions on straps or material to make them out of? Seems like most auto parts stores have them for $5-$10 each.

 

Make your own.
https://www.ebay.com/itm/5-FEET-3-4-...MAAOSwl-FZkFZ3

 

Now that's what I'm talking about. How thick does it need to be? And how heavy do I need the terminals to be? I'll have to stop by a hardware store and see what's available.

 

Most new TSS are POS. The plastic they are made is not ridged enough and the contacts are not of a solid plane to make contact. You can try to slip a points file in there to even out the contacts.

 

I think they taught that method at PO school! Seems it was a very common practice though, when these trucks were fairly new and still regularly out on the road or the farm.
Just like putting larger and larger glass screw-in fuses in your household wiring. Hey, when one blows, just put in a bigger one!

There may not be any. Might not even have been any from the factory back then! Or at least a minimal number of them, as they didn't take trucks all that seriously sometimes back then.
But as said, add your own. This is a good time to upsize what you would have gotten from the factory anyway.

You're not going blind. They probably are not included.
I've seen many factory books that said right on the cover "wiring diagrams included" that weren't. I think it's semantics though. They put diagrams of where the wires are in the cab, but not real schematics of what they do or where they go.
All too common an issue with the seventies and eighties trucks. Maybe the same with sixties.

That copper braid stuff is cool!
Did not realize the premade ones were getting so expensive. Still see them on the HELP racks and they are quite helpful.
But they do not have to be braided if you don't want to, or don't want to pay the price. Any wire will do, with 10ga probably being the go-to size for this.

If your battery cables were ever replaced with standard off-the-shelf stuff from most stores, they probably used single cable types with no additional mounting points like they would have from the factory. So I always recommend that whenever buying new cables, get not only the larger ones (2ga is great stuff!) but get the ones for the battery with the extra "pigtail" for additional connections. For the ground wire, this would mean that in addition to the large cable for the engine block, there is a short length of 10ga wire with a crimp connector already on it.
So with a little bit of 10ga Black wire and some ring terminals you can really go to town on the rig.
Typical locations:
1. Battery to block. The closer to the starter motor, the better.
2. Battery to body (fender near, or at the starter relay is a good spot. If yours is the type with the battery tray mounted to the firewall, the body behind the battery is a good spot.
3. Back of engine to firewall. Cylinder head, or intake manifold, or valve cover bolt. Try not to use the main mounting bolts for something that needs to be carefully torqued, such as an intake (V8) or cylinder head. A valve cover bolt for an inline-6 would seem a good spot.
4. Engine to frame. Not really as critical as so many others, but it still seems a good practice.
5. Cab to frame (jumpering the body insulators basically). My '79 has two or three braided straps clipped to the sheet metal at the body mount, then to the frame mounting pad.
6. Metal dash AND instrument cluster to firewall. I like to use a common through-bolt for grounding the engine to the firewall and dash accessories to the same bolt. But you can do anything that gets the ground connection.
7. Ground the hood to the rest of the cab. Really for in case you mount a hood lamp, but I think it serves to reduce radio noise too.
8. Just in case, I ground the core support to the fenders. Helps the headlights, turn signals and usually the horn, and anything else mounted there. This practice comes from having trouble on the old Broncos. I don't think it's as big a problem on the pickups, but I still think it's a "best practice" kind of thing.
If nothing else, it could be great for the headlights!

Some of these may just be helpful for reducing radio noise, but in general things just work better when everything is grounded (bonded) together.

Good luck!

Paul

 

All good suggestions, if perhaps a tad overkill. If the objective is to eliminate radio interference (RF), then it would be better to use one of the braided copper straps. Surface area is needed to shunt RF to ground. The distributor is the worst offender for RF noise, continuously wizzing arcs in 360 degrees. Braided strap(s) from the body where the radio is mounted back to the battery will be you're best solution. The hood will generate a static charge from driving, especially in dry dusty environments, so a strap from the hood to the firewall will allow that to bleed off instead of arcing which generates RF noise. The old AM radios were much more susceptible to static noise than an FM radio, but it will still benefit from reduced RF noise. And of course to get a good ground the attach points need to be bare metal.

It's interesting you mentioned "bonded". In the aircraft industry, bonding refers to a specific level of resistance between two structures. Class R bonds are specifically for RF (and also used for lightning protection). A class R1 bond is 2.5 milliohms or less. It takes a special tool to read that low. Class S bonds are for static discharge; less than 1 ohm. Pretty much any decent multi meter can read that. But there is a difference between a DC bond and an RF bond that even a lot of engineers don't understand.

 

I agree most turn signal switches are garbage. I chased my stop light and turn signal issues for weeks until I broke down for a new TSS harness from Dennis Carpenter. Changing that and my stop light switch itself, fixed my issues. If you don't have a mechanical switch on your brake pedal, get one. The fluid type switch on the brake master cylinder are notoriously unreliable. A little bracket on your brake pedal and re-route your brake light circuit through it will clean up voltage on your tail lights. I ran braided stainless ground straps on my truck too. Cylinder head to firewall and one from head to frame. I ran the battery ground to a welded-on bolt to the frame. The only other issue to check is how clean each individual light bulb is connected in your 50 year old light sockets. Basics will go a long way to sorting out frustrating problems that are intermittent like yours seem to be.