Cars dies after new alternator...

[beefsteak]

I'm at a loss...

I had our '03 Protege die and was able to charge the battery on my home charger. Had the parts store test the battery, and results were a good battery. As a result I decided to change the alternator. Well, after installing the new alternator I started the car and ran it to test the system. After 30 mins it died again; dead battery. Anyone else run into this? What else can it be? I'm thinking of changing the battery now even though the test showed it was good.

Thanks for any assistance!

[Ace]

check your connections, find out a voltage reading while the car is running. should be 13.5-14.5ish.

[D323]

bad alternator out of the box is possible. Especially on a reman.

[1Mazda323Fan]

Definitely check the charging rate with the car running, as stated it should be 14V plus or minus a bit. I'd lean towards a bad alternator, though, since the car doesn't run on the battery. It's only there to start the car; once it's running, the alternator supplies the power for everything. Check all the wiring that you can see, making sure that no wires are touching each other or metal where they're not supposed to.

[beefsteak]

Well, here's an update...
It turns out it was the battery, even after it tested as "good." It was holding a charge but with the accessories on it could not keep up. I tested the alternator again and it tested fine. For some reason the power was being lost over the battery through an inefficient chemical reaction possibly? I always thought the alternator "bypassed" (for lack of a better term) the battery when it was running and only really needed for starting the car. Oh well, live and learn. Replaced the battery and now is running fine.