99 Expedition Charging System Problem

A few days ago my wife had a hard time starting the Exp. it would just click and then it started. When she got home I started it a few times and it kicked right over. The next day, it was good, until later in the evening when it did the same thing. I went and bought a new battery and then we drove to Fla. All went fine until I was in a parking lot and tried to start and got just clicks. The new battery was dead. So, I bought another. At idle, we only see 12 volts at the battery, but I had AutoZone check it and they tested it at 2500 RPM and said that all looks good (14v). If I remove the pos. terminal when the car is running it dies. This has always been a good test for me. What could be the problem besides the alternator and how do I test for the problem. I would think that I should see 14v at the battery when the car is idling? Help.

Make sure all your grounds are ok.

Okay first thing NEVER pull a battery cable to test an altenator on a newer vehicle you will fry your ECM. Next it seems you are lacking AMPs instead of volts! yea 14 is good but, how many amps is the altenator putting out under load?

Look at the windings in your altenator you can see them through the case they should be red if they are black or burnt looking then the stator is bad!
meaning your not getting ampage that is why your new battery died.

You may need a new altenator.

I changed the alternator and all is good. Thanks for the assistance.