So, I was warming up my f-350 7.3 when all my lights radio and heater went out for about 3 seconds n when they came back on the vent blew smoke in my face. Upon checking it out I found the fusible link on the right fender was burnt up and the entire wiring harness is now ground out. Anyway I was just wondering if anybody had any ideas on where to begin my search for the problem.

 

Whatever device or circuit the visibly burned fusible link controls would be my first point of diagnosis.

Something has caused it to open---why needs to be known.

 

What I would do is leave the burnt fusible link disconnected, and then see what works and what doesn't. Then report back and also tell us what year truck you have. We might be able to look at the diagrams and see what circuit has the problem.

Another clue where to look is previous modifications. The factory wiring harness is pretty good, and rarely if ever fails. When it does fail, it's usually at connections and modifications made to add aftermarket stuff like stereos, lights, alarms, etc. So if you have anything added and it's now not working, that would be a good place to look.

 

Sorry, the truck is a 2000 f350 powerstroke.Burnt fusible link is the main cable that goes from alt to the starter relay and to charge batteries. Now the entire wiring harness is grounding out, I used my multi meter connected to positive battery post and anywhere I put it on the harness I get voltage. I cant find anywhere on the harness that looks like its burnt thru and touching metal so I was wondering if its possible for any of the relays and sensors could possibly go bad and ground out. I realize I'll probably have to replace the harness but I was hoping someone might have an idea where to start looking for the source of the problem.

 

Oh I should also metion that the cable post on the alt was also ground but the cable remained ground after removing the alt

 

I get the impression you are a newbie to electrical, or it was just a typo. Reading between the lines from your last two posts, you are reading ohms? Not voltage correct?

If you do have your meter in ohms mode (measuring resistance), yes you will always get a reading through the harness. There are many many devices hooked to the harness that draw power all the time, and will give you a ohm reading. The memory in the radio, the memory in the various computers that run the truck, etc.

And yes if you put the meter on volts, you will always read voltage on the harness in certain places. Mostly at the front of the harness at the alternator where you are at.

I would check both batteries and their condition. If something happened to them, it might have pulled too much from the alternator and burnt the fusible link. Check that charge wire and wiring around there also. If you find nothing, replace the fusible link and then check the charge voltage with the engine running. It should be no higher than 14.5v. If it's a lot higher, then I would suspect something is wrong with the alternator.

 

No I'm reading voltage not ohms. Multi meter red wire on positive battery cable and black on alt cable reads 11 to 12 volts and like I said if I touch the alt cable where it is supposed to be connected it arcs like a sumbeech. So, something is making it ground out and was just hoping maybe someone knew of a known problem with a relay or sensor because the wiring harness is very expensive even used so I dont want to put a new one in just to have the same problem. Im fully capable of checking it all out but was hoping for a lead or two.

 

The wire that is burnt goes to the alternator only? And that's the one that arcs when you touch it? Then it would be that wire or the alternator faulty correct? If that is correct, the truck should still start and run normally, just not charge. If it's the wire I am thinking of, it's only the charge wire, nothing else.