I have a 2008 F250 Super Duty. The wife went to start it Sunday and said that sometime caught fire and smoke came out the driver side wheel well. She said it smelled like wires burning. When I got home I looked it over and did not see anything obvious so I started it up and it ran fine and looked like every thing worked OK. I could smell some residual odor that might be electrical. Next day I went out and looked more closely and saw nothing new. I started it up and let it run while I looked and sniffed. I got in to turn it around and heard a noise start up the sounded like the noise a radio would give from engine noise. I shut it off then tried to restart and just got a flutter clicking. Checked the voltage of the batteries and they read around 8.5v (Wow). I pulled the positive leads and rechecked, slowly coming back up to 12v. I have fully charged the batteries now and tested current draw for each positive wire. One draws about 100A with the key off (I think that is a problem). The question is: Does anyone know where it goes? Maybe the alternator fried?

 

Well, it sounds like a dead short to ground, but that is overstating the obvious.

You have dual batteries, so we should assume you have a 6.4L Power Stroke Diesel?

 

Yes it is the 6.4L. That picture is from the passenger side.

I hooked up all but that wire and the truck starts and runs.

 

I would start by going over every inch of that positive cable to see if it is rubbing somewhere and has worn through the insulation.

I think it goes to the starter motor, but I could be wrong there.

 

No, not the starter. The truck starts and runs. Tested this morning and while running the charge voltage was only 11.8 so I think alternator. Very hard to follow things in that tight engine compartment.

 

Well, the alternator could have been damaged by the short circuit, so it doesn't surprise me if it isn't working, but I still think you have an intermitant short in the positive battery cable somewhere

 

You don't think the alternator could short out? Anyway I will see if I can find the alternator and disconnect it and test that wire again.