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Oh man, I have two electric volt meter things.... and still have no idea how to actually use them! :-( Electricity is like looking at a spreadsheet, my brain starts melting down quickly.
I'm taking today to try and trouble shoot then might call in a pro :-( but fingers crossed today fixes it!
I would test the fusible link with ohm meter, zero or close to zero resistance, it's still good, anything higher than that I would replace it. I'd have to dig out a wiring diagram but I believe there are more than one fusible link. One to the ignition switch, one to fuse panel and maybe even one to the voltage regulator from the alternator I seem to recall. I wouldn't replace the regulator until I've checked all the wiring and eliminated any potential issues there. Doing some resistance testing is free. Just set your multimeter to ohms or what looks like a horse shoe symbol. If you got a needle or safety pin you can use that to pierce the insulation and touch probe to that or attach an alligator clip if there is no other way to connect with the wire. Best of luck, troubleshooting electrical is tedious to say the least
Fusible links aren’t the same as fuses. They can tolerate a high current draw for a set amount of time (depending on their length) whereas fuses cannot. Exceed a fuse’s amperage rating by even a fraction of an amp for a millisecond and it pops. Fusible links won’t. It takes their “cup” longer to fill up before it overflows. Trying to come up with analogies here that might make sense to you…
Anyway, install the correct fusible link back in there and let us know what you find.
If you’re going to use a fuse, use one of 40 amps or larger. Preferably 60 amp to cover all bases.
You’re protecting the wire, and it’s a 10 gauge wire so you should be fine.
The 14 gauge fusible link is two gauge sizes smaller than the wire protected. Four numbers smaller than the wire, but two gauge sizes.
A standard small holder probably doesn’t have the wire gauge sufficient for this load. So along with a 60 amp fuse, get a heavy duty fuse holder. The maxi fuse style, or an even larger more robust, mega fuse, or midi fuse type.
The alternative, of course, is do as mentioned and install a new fusible link.
They are usually readily available on the HELP rack.
Thanks guys!! I rushed and read the link as 14amps - not 14 gauge.
this makes more sense.
Just ordered some fusible links and hope this gets it all fixed
Thought I'd add some more details to clear (hopefully!) some things up.
Originally Posted by turtleheadtim
So, upon inspection, I can't find an engine to frame ground - so I'm adding one today.
It's a good thing to do. But just so you know, I'm pretty sure that there never was an engine-to-frame ground from the factory. Just the engine to firewall, in addition to the battery-to-engine and battery-to-body.
Originally Posted by turtleheadtim
The negative terminal on the battery goes direct to the engine block. That's the only ground/where all ground is made from (aside from the speaker wire which goes from the battery terminal connector into the cab (hunting down where the speaker wire ground ends at)
From later info, it sounds like the speaker wire was the ground for the aftermarket radio. Common practice to put the power and ground for an amp directly to the battery to reduce noise and to get full power to the radio. If not using a separate amp, it was probably just what the installer felt was a "best practice" (it is) to reduce noise.
Originally Posted by turtleheadtim
Here's the requested relay pic:
I know you meant regulator.
The location is consistent with being a '74. Sometime later they were mounted where it was described in the previous post, over by the horn relay on the fender apron.
The three positions of wires indicates it's for an ammeter-equipped truck. Consistent with your later cluster pic.
The capacitor thingy bolted to the mount is a factory noise suppressor.
The Black wire attached to one of the regulator mounting bolts is the alternator ground and should run all the way over to the alternator case through the harness. In some cases (most?) the ground wire is not visible at the alternator because it's actually attached to the metal ring that is used to bolt the strain relief to the back of the alternator to keep the wires organized and safe from spinning thingies and hot stuff.
Oh... funny enough, the horn works (I think the picture makes it look like it's not plugged in, but it's on the post)
Good. I think I can see it now. Sure looks hanging off to the side!
Originally Posted by turtleheadtim
Regulator is in the above picture - mounted next to the radiator at the front of the truck (had no idea what it was til you mentioned it - should I be looking into replacing it?)
No! Not if it's still working that is. If your alternator is not charging the battery however, it will be worth looking at sooner rather than later.
Just out of the picture is another item that was on early trucks from the sixties to early/mid seventies. I never played around much with the regulator systems on these, and it's not how the Broncos were wired right back to '66 so not sure why the trucks got this different setup. Maybe someone here knows what exactly the differences are, what that thing does, and whether or not the actual regulators are the same between early and late. Although a parts search would yield that basic info about whether it's the same.
Looks like an original, or at least older replacement. Back in about '74, Ford started changing out to the "electronic" style, rather than the original "electro-mechanical" style with points and resistors and all sorts of things you could fiddle with and adjust. In the early days, you could tell the difference by how tall the regulator cover was. Yours is a tall one, and the electronic version was about half as tall. But at some point, I think they all became electronic and for awhile you could get the "old" tall style in the new electronic version. Not sure if you can even buy an old points type anymore, but you can still get the old looking tall regulators for those that want to look original.
A member here just a couple of weeks ago replaced his entire assembly with a later model one to simplify his setup. Just a regulator now, without that secondary thing over on the fender.
Originally Posted by turtleheadtim
Just checked the speaker wire, looks like it runs ground from the battery direct to the aftermarket radio. can't imagine that would be the wire to chase down further? (I didn't pull it all the way, just found it connected to a bundle of wires that all lead up to the back of the stereo - but if you think it could cause the problem, I can pull it all out to check)
Nope. No need.
It's for the radio, and (hopefully) nothing more. And that can't cause a no-crank issue. If it had anything to do with the starter, it would likely have melted the first time you turned the key to START.
But speaking of grounds again... If you don't have a battery to body ground, you should add one now.
The original was grounded to the engine with the big cable (like yours) but had a secondary 10ga wire bolted to the body. Many aftermarket battery cables come with this secondary wire, but I'd have to say that most don't. So many owners will end up replacing their original cables (and rightly so!) but with one that does not have the body ground.
Best practice for you is to add one. You can literally bolt it to anything that looks like a body bolt on or near the fender. One of the starter relay mounting bolts is a common point. I think the original was one of the top fender bolts right beside the battery?
Originally Posted by turtleheadtim
and here's the dash and fuses:
Is that a fuel tank selector switch? Dual tanks? Still have the mechanical valve under the driver's seat by the door? Or was it replaced by an electric switching valve?
Maybe the switch just changes the gauges and you have to flip the lever on the floor?
Originally Posted by turtleheadtim
Nice fuse panel!
For it's age (and being in a truck after all) it's actually in fantastic shape.
But you can see the rust on the stop lamp fuse. I think I mentioned it in a previous post, but if not, you should ALWAYS take glass fuses out to wipe them clean at least every other year or so. It's not a lot of work and well worth it once in awhile. I do it once a year now that I've had so many issues resolved by this simple maintenance item.
In your case however, a little cleaning is not enough in a couple of those lower fuses. You will need to scrape them carefully, or wire brush them, or whatever you can think of. Use electric grease (carefully) or di-electric grease (less carefully needed) when you reinstall them to keep the future rust at bay.
And speaking of fuses, fusible link capacities, and such...
Notice that even just one of those fuses has a higher capacity than the 14a fuse you installed in the main line. The reason I mentioned 40, or even 60 amps as a good rating for the main line, is that it has to power up all the accessories and not blow. Heck, just the stop/tail/turn fuse is 20A! The heater is 30!
Ultimately, if you add all the accessories together, you want circuit protection that can handle all of it. Some dark dreary winter night you might have the high-beams on, the wipers going, the hazard flashers turning all four lamps on at the same time, the heater going full blast. You don't want to blow your main link just because one of the kids decides to honk the horn while you're clearing the road!
Even though the fuse was not in that particular wire as far as I can tell, YES, the alternator can blow that fuse.
I know you've already figured out that the fuse was not big enough because you were thinking "amps" rather than "gauge" at the time, but just going back to this, if you have an alternator that is capable of putting out 50 or 60 amps, then yes, it's going to easily blow a 14 amp fuse.
Just as putting the fuse in the main power wire to the cab blows quickly because many of the accessories that you normally use are able to draw more than 14a as well.
You just weren't used to dealing with this stuff is all. But if you think it through (without your brain melting!) you just need to notice what loads are on a circuit, what wire gauges the circuit encompasses, and work from there.
Next time....
Oh, and as you have found out with your fuse experiment, you were not getting power to the cab and ignition switch, which in turn means you can't put power out to the starter relay to engage the starter.
It worked momentarily, so your experiment was a success!
The voltage regulator and alternator have NOTHING to do with a sudden no-start condition. Not at least while you're reading a fully charged battery. All they do is keep the battery charged and power everything else, but only after the engine has started.
If the battery is not dead, then a no-crank situation is not the charging system.
If you're not getting power to anything, it has NOTHING to do with the starter relay. Think about it. The relay is certainly the common thread there, being in the middle of it all. But the battery cable is literally in physical contact with the main power wire to the cab. So the relay is nothing more than a convenient stud to mount them to.
So while the battery cable and cabin power wire are in contact, the relay is not in play. Only the wires themselves are suspect. Connections, fuses and fusible links, splices, and anything out of the ordinary. That's where you look.
Lots of little simple tests you can do when different things fail. Some items are hard to test, such as a Dura Spark module. Others are easy, such as starter relays, Dura Spark distributor stators (magnetic pickup) and such.
Don't let wiring be the death of you. Or cause to pull too much hair.
Have fun!
I have a new fusible link arriving today (6 of them cause I fear the worst and would rather have spares)
Going to pop that in and fingers crossed my favorite truck is back in business.
On the battery front, I've replaced both battery terminal cables - and, I picked one with the tail on it, so I will ground that to the fender today.
Yes, the truck has dual tanks - and that is the switch for it - BUT the switch doesn't do anything, I think it's disconnected/unplugged at the switching valve - no idea if it works.... is it worth just plugging it in and see if it does anything?
I'm afraid to even open the second/rear tank - I fear it's the next project I don't need to add to my list to clean out, but it's a large all metal tank - no idea if it's lined.
That said, my fuel gauge doesn't work - need to trouble shoot that at some point. In the meantime, I just drive around with 5 gallons of gas in the bed at all times ;-)
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