ok here is what i have 01 2500 5.9l cummins. is the alt. suppose to put out 34 volts when it is unhooked from the 140 amp fuse link? what is happening is when hook it back up to the fuse link the wire from the alt. starts to melt down and the voltage drops to 14.3. now i was wondering if the alt. is bad?

 

I beleve 14.3 volts is the normal output of the alternator while it is charging.

 

Yes, 14.3 is normal. If wiring geting hot, there is too much resistance in wire or terminal where hot or has heavy charging load. May be heating elements engerized and pulling 200 amps or so. Dead batteries generally are not enough load to heat up wires unless internally shorted. One could be, so disconnect one and try, then test the other. Remove alternator and have bench tested at parts store.

 

Sounds like the same problem another guy on here had. The + output lead from the alternator was shorted in the front of the engine block somewhere. He just ran another 4 gauge cable piggy backed to the existing, Quick fix. 4 gauge is the same size as a smaller battery cable with crimped lugs on it so you could pick one up just about anywhere for under $15.

That least I think it was 4 gauge.. its in the wiring diagram manual, anyway just get one the same size.