I have a 03 7.3 250 I had a post about a fuse blowing and figured that out but I think the root of the problem is somewhere in the wiring. after replacing the fuse it blows every 2-3 days Truck quit starting turns out to be alternator I pull the alternator I purchased 18 mths ago from Napa and on the back of it where u bolt the wire to it is pretty much all but melted. I dont know if it could be alternator shorting out blowing fuse or power surge blowing fuse and shorting alternator. The only Idea I have is too mount on the new alternator tonight and see if the fuse starts blowing again because the fuse does not blow when the alternator is dead anybody have any ideas? Thanks

 

Hey Beng, sorry to hear you're still having problems but looks like you are tracking it down. When you say the back of the alternator looks melted, are you talking about the alternator connector or the wire from the harness? Has someone replaced the end of the wire with a connector that is too big and is shorting against the alternator housing?

 

The bolt that you put the connector over is what melted along with the little area around it I will check and see if the harness is to big tonight when I install the new one tho.

 

Melting comes from heat, which comes from high current demands.

The first place I would suspect is your batteries. An intermitant internal short in one battery will do this, and can be a bugger to find.

I struggled with an internal short in a battery for about 18 months on an old F-100 I used to drive. I'd be driving down the road, then everything would shut off. Let me tell you, that was tons of fun on a dark and rain filled evening! I'd pull over, 5 minutes later everything would come back on and act like nothng happened. I finally figured out it was the battery after I had replaced most of the wiring (1956 F-100 wasn't very complicated), ignition switch, generators, voltage regulators and ammeters. I swapped the battery with one my dad kept in his garage for a travel trailer, problem went away.

Now, if one of your batteries is doing this, it won't shut down your truck but it will draw very high current from the alternator and the other battery.

 

Good point my auxillary battery was dead I have now replaced so I guess all I can do is replace the alternator and see if the problem continues or not.

 

And resistance. If that connection was bad to begin with, it would melt when a high load is drawn through it.

I'd almost think that either the battery going bad caused the high load, or the regulator went bad and is in full-charge mode and melting that connector (and causing that an already marginal battery to go bad from overcharging).

Changing the alternator changes the regulator too (it's on the back of the alternator), so after fixing that cable, it sounds like you'll be good to go.

Let us know how it works out.

 

Since I replaced the alternator I have had none of these problems everything is back at full capacity. Thanks for the info

 

Thanks for reporting back!