78 F100, 300 i6, went out today to fire up the old man, but nothing. Batter is over 12v. No horn, lights, etc. what gives? Was getting dark, didn’t get to look around much. Any ideas? Thanks y’all!

 

if the battery is really at 12v, then you have a bad connection or bad battery cable. remove both battery cables and clean inside as well as the battery post. Make sure the other end is clean and tight at the solenoid and the engine block...

 

Thanks for the reply, already did that stuff. That’s why i’m at a loss. I will look at the fuses in the morning.

 

ok, you stated you didn't get to look around much, so I started at the top....why don't you help us out by letting us know what all you've tried....
Fuses aren't causing your totally dead issues...

 

could have lost power at the selenoid

 

Fusible link I would think, but the horn not working kind of refutes that. At least on my truck, the horn is wired straight to the always-hot post on the starter relay/solenoid, without a fusible link.

When my fusible link blew, NOTHING on the truck worked, but I didn't think to try the horn.

It could be the ignition switch or its wiring, too.

 

Sorry guys, I got a little sidetracked. Ok, so just prior to my original post, I looked at the obvious things in the vicinity of the battery- cables, tight connections, etc. I did not check the connection at the starter, but I did that today, it’s good. Took the battery out of my Jeep to rule out battery, still dead. Im Leaning toward the solenoid, but not too sure about the fusable link... how can I rule that out? Thanks all for the replies!

 

You say everything is dead in the truck? No power to anything? The solenoid won't cause that, but a fusible link sure will. The fusible link(s) just happens to be very near the solenoid.
Follow the positive battery cable from the battery to the solenoid. You should see two or three other wires which are secured to that same terminal post as the battery cable. On my truck, the horn has it's own lead with no fusible link, and the wire is yellow. I forget the other wire colors, but follow those other wires away from the post on the solenoid, and you should see at least one where the wire passes through a little rubber block. That's where the fusible link is, and you can test for continuity through it.

 

thats! I’ll check it out!

 

New developement- When I connect the battery and try to crank the truck, i can blow the horn, but that’s it, NOTHING else works. If I turn the key to crank it, I hear a small clunk (possibly solenoid?) and then Nothing, not even the horn will work. Disconnect the battery, reconnect it and the horn will work again. Hmmmm

 

Sounds like a classic case of a dead battery cable. Either positive or negative will do it, but in my personal experiences it's always been the main positive cable from the battery to relay/solenoid.
And by "dead" I mean it has failed and it's not capable of being tested by normal means either. An ohm or volt meter can't test it, because they only draw a fraction of an amp to test, whereas the starter tries to pull well over 100amps through the compromised cable(s) and literally breaks the connection temporarily until you manipulate the cable. Eventually it will just stop self-healing and die altogether. So I recommend changing them both.
And you can't go by new vs old either, as the first one I experienced was just shy of three years old and of visually at least, high quality manufacture.
Oddly enough, I've never had one of the parts stores cheapy cables fail like this. Only the fancy more expensive parts store supplier types.

This is one of the reasons I usually cite for overkilling the cable size when you buy new ones. If a 6ga lasted thirty years, a 4ga might last longer. Then a 2ga longer still. Or if it does not last longer, at least it works under heavier loads more easily while it's still good.

What age and condition are your cables? No matter what though, since it's cheap insurance and easy to replace, I'd replace all three of them with new 2ga versions just to see if that fixes your problem.
If it does, then great and it was totally worth it. Even if not, it's still nice to have new heavy duty battery cables and you're only out a few bucks.

Good luck. Hard to say what it's going to work out to be, but obviously my vote is a bad cable.
You could even replace one at a time (Like I did the first time) just to see which one is the culprit.

Paul