Hello I've Got a problem

1. my battery light on the dash came on and the voltage gauge was jumping up and down with a/c, power windows and the loke. I went to AutoZone (parts store) and had them test it. result was a bad alternator.
they didn't have one instock so I went to Checker ( parts store) I had them test it and they siad bad Battery. they Had an alternator and Battery in stock but way to much.
I went Back to another Autozone and got both alternator and Battery. replaced them and everything looked fine.

2. one day later and the battery light is not coming on but the voltage gauge is doing the same thing. battery is not charging and my engine died on the hiway.

History
2000 ford f150 xtl
115,000 miles


what do you think it could be?

any help please

 

Wiring. Check the voltage at the alt. and then at the battery terminal. How did the wires look?
It could also be a defective alt.

 

With my F150, I had an alternator that died intermittantly. It turned out to be the rectifier in the Alternator, which I replaced with success. The battery would register as low if the alternator was bad. You may want to check the harness to the alternator, as a short would to the rectifier or the voltage reg in very quickly.

 

absolutely a wiring harness problem.