my thunderbird battery is dying

first off, i know nothing about cares and really need help!!!! while driving my 1990 thunderbird everything slowly died, from windshield wipers then finally the car. A nice man jumped my car, he said it might be the alternator, but he check some output (see how cluless i am) and said that seemed to be fine, to just clean the currosion off the battery. I did so, and got another jump. This time within moments the cars battery light went off, and started fine 2 times afterwards. The next day i went out to start my car, and it was dead again. so is it the alternator, or do i just need a new battery. I have no clue. Thanks for any help!!!!!!!!!!!!

check your battery posts for corrosion (Anything that is built up on them, normally a green or white color). If they are loose or corroded, it could cause the connection between the battery and car to be too weak to start.

Your local Sears or Autozone will test your battery for free. Ask them. If your battery is over 4 years old it's a good bet it's time to replace it. If the caps on top of the battery are removable CAREFULLY take them off (to avoid getting acid on you or in your eyes) and see if there is water visible in each of the six holes. If no water visible the easiest thing to do is buy a new battery. You can add distilled water and charge the battery but it probably won't last long.

Its Probly The Battery...have It Checked...make Sure The Cables Arent Corroded

I have a '96 LX and the battery is prone to drain in the middle of the night, leaving the car dead as can be in the morning. I've had the battery replaced twice, and the cables are in good shape, yet the battery problem remains. However, i am led to think that it has nothing to do with the battery, because the car starts fine as soon as jumper cables are hooked up--as though the battery doesnt even need to charge. And even after a 20 minute ride the car wont start again after the engine is shut off. Does this sound like an alternator problem? Any feedback would be appreciated.

Yes. If a diode is shorted it will allow the battery to discharge through it when the ignition is off. Have your alternator tested.