i have a 2004 f350 4x4 6.0l diesel. The alternator has been changed 3 times in less than a 4 month period. I installed a new pigtailed harness for alternator along with a motorcraft reman alternator from ford last month also replaced one battery. It is back again with same problem. The alternator heats up very quickly within a couple minutes after cranking. I have also changed the other battery as well. It has 2 interstate 85 month batteries now. Also it has a aftermarket banks turbo installed as well. The coolant appears to boil out of degas tank on occasion. I do not know if this is related. But from a cold start, the alternator will heat up in a couple minutes. Any help is appreciated.

The alternator may be heating up because of the condition of the old battery. Most auto parts stores will test and charge batteries for free.

My bet is that the old battery is so discharged that the alternators are burning out try to charge it. It's likely a bad battery with high internal resistance. This link should help:

https://www.askmehelpdesk.com/cars-t...ml#post1973613

The overheating problem is separate. These links should help:

https://www.askmehelpdesk.com/cars-t...ml#post1923468

https://www.askmehelpdesk.com/cars-t...tml#post235973