Sorry for the long post and non technical description, I am posting for my husband. i will start from beginning. this is our first diesel. few month back our starter connector broke, so my brother in law came and ran a battery cable (4 gauge?) from positive to starter (yes i know now that was bad, to small gauge). we drove it like this for a few month and yes the battery light was on, steering pump went out and when we fixed it we realized it was burning up and welding to the positive terminal,friend said it was nothing. fast forward 1 month. truck was driving fine, didn't drive for a few days went to leave and would not start, husband looked at it real quick cleaned the terminals( we had problems in the past of them not connecting) positive terminal was poping and smoking when trying to start, so he said we need the new cables, got the positive battery cable harness from wrecking yard, put it on. still wouldn't start, realized it was out of gas ( yes my fault, i know, read over 1/8th ) filled it up,cranked it for a bit, started up drove to the gas station, (15 miles there turned her off started her up twice) filled her up came home thought all was fine and the battery light was off. while changing the battery harness husband realized we had some burnt up fusible link to the starter solenoid(?passenger side) so he replaced with regular wire. next morning he drove it to work( early morning) he barley made it 10 miles and it died, not charging. next day he took the charger to work and charged it, drove it home 10 miles was fine but didn't have light ect on. Replaced the one wire with fusible link and fixed also a ground cable that was burnt up, and discovered the fuel filter heater sensor was burnt up. called junk yard and got new fuel filter housing, switched over heat senor and a few other things, put fuel filter housing back on, jumped it with the car, and went for a drive. still battery started dropping again, replaced alternater with one we picked up from the wrecking yard when we got fuel housing, started the truck and sat and watched as the batteries died, husband has no idea what to check next can you give us some ideas as to what else could be causing it to not charge. we have been charging the batteries daily with our charger to start it while doing all this.again sorry for the non mechanical description. thanks in advanced. we love this truck she has been great(2yrs), minor problems until this.

 

Pull the alternator, and have a parts store check it out.

 

I am actually taking the original alternator in right now along with the batteries to get tested. we tested with a multimeter and they tested fine,

 

bought brand new alt put it in still not charging? what now?

 

See if there's any power getting to the smaller wires going to the alternator.

 

he's already got the harness pulled out and going threw it.