My 2002 7.3 quit charging and I verified that there was no charge going to the batteries. Had a look today and on the passenger side battery, there was a melted set of wires attached the side positive post. Do these route back to the alternator? Or part of the fuse system? Or did my alternator start putting out to much voltage and melted the wires? I uploaded photos but I'm not sure how to get them to view on the thread.

Attached Thumbnails

 

 

New update, pulled the alternator, had it checked and it grounded itself. Therefore it fried what I assume were the fusable twin wires right at the passenger battery post. Ford spent 15 min and could not find the part and all they wanted to do was replace the harness. Napa drew a quick blank. Does anyone know the part # or gauge of fuse? Can it be replaced? In Canada, so does anyone know where to get one? Can I install myself, because I didn't think it could be soldered, only crimped.

You probably have an 8 gauge battery wire and a 12 gauge fuse link. If you can't find any fuse wire you could use a maxi fuse.

Here's the info on fuseible links from the 99 Service Manual

Fusible links are short lengths of wire that are smaller in diameter than the wires they are protecting. Fusible link wire is covered with a special thick, non-flammable insulation. An overload condition causes the insulation to blister. If the overload condition continues, the wire link will melt. To check a fusible link, look for blistered insulation. If the insulation is okay, pull lightly on the wire; if the fusible link stretches, the wire has melted.

When replacing fusible links, first cut the protected wire where it is connected to the fusible link. Then, tightly crimp or solder the new link to the protected wire.

Fusible links are often identified by color coding of the insulation, as shown here:
The circuit diagrams show all the charging system fusible links as 12 GA, Gray.
This is from a 99 service manual, but I'd be surprised if other years had smaller fuseible links.

You should be able to get fusible link wire at about any auto parts store, although I've never tried. Not surprised that your Ford place couldn't find them. They probably get them in a kit with an assortment of sizes/colors, and the guy was probably looking for a part #.

Yep your right. It is grey and the wire has melted. Found some fusable links at the auto parts store. You would have thought that considering an alternator usually goes at some time or more in a trucks life, and a large percentage will short, causing the fusable link go, they would have come up with a better way to replace that link.

The fusable link is a cheaper alternative to a circuit breaker or high-amp fuse. And, it takes more careful repair to replace than either of the other two methods which forces shadetree mechanics to search for the short rather than just resetting the breaker or replacing a fuse.

It is rare to have to replace a fuse link when an alternator fails. It's just a guess but I'd wager a Big Mac and fries that there are at least a thousand alternators replaced for every fuse link. I have rebuilt dozens of alternators and I can't remember ever replacing a fuse link at the same time.

just did a search on this, thanks for the info . Batteries were not charging batt light was on , fusible link melted, thinking of putting in a 50 amp max fuse, because I can't find the amp rating of the link , and I'd rather replace a fuse than the wire.

I think your idea of just using a 50A fuse will be problematic when the alt puts out much more than that. You would be much better off getting the 12g grey fuse links and using them. They are not as difficult to replace as you think.

Agree totally with tinman.

Considering that your alternator is rated for 110 Amps, even two 50A fuses in parallel would probably fry pretty soon.

e94Racer
So what fuse size amp worked? I have the same issue and can't find any solid answers.
Thank you

The answers are above: Replace the fusible link wire.