Good addition to the thread.I just recently had a situation with my father-in-laws 2003 6.0. We get in a try to start it up. It immediately sounds like weak batteries. We replaced them. Tried again and sounds like weak batteries. We changed starter and try again, now it spins a little faster, but no start. To make a long story short, We took the serpentine belt off and it starts right up. The air conditioner compressor bearing was locked up.