I am having the same problem with My Ford F150 4.6... I bought a new Alternator and a new battery but all the gauges go wild and the truck quits. If we boost it then it starts but other then that it wont start on its own. We didnt try the harness yet so I hope that is all it needs so I can get back on the road again.... Do they sell the Whole Harness?

 

Your problem does not sound like the one in the old thread you piggybacked onto. So, I'm moving your post to a new thread.

Just for your information, the alternator has nothing to do with starting the engine. It's there to restore/maintain the charge on the battery.

Try to be a bit more specific about the symptoms and someone like SSCULLY will likely be able to help you diagnose what's going on.

- Jack