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Held car dies! it!

i have a 1985 buick skylark. i replaced the alternator and the battery and for some reason the battery wont hold a charge and stalls the car after jumping. what could this be???

Have you checked the battery? Have you had the charging system checked? Hoe old is the battery?

yes the battery is brand new and no i did not get the charging system checked.

I would put the battery on a charger to make sure it gets a full charge. A good charger will also tell you if the battery is defective.

And I would check/clean all of the alternator connections & battery cables & such being sure not to miss the grounds. Hook it all up, start the car, and stick a voltmeter on the battery terminals. You should be getting 14V or so. It is possible that the new alternator is defective, but it is even more likely that you didn’t need a new alternator to begin with. The problem is probably located between the alternator & battery.

Charge the battery. Start the engine and, using a voltmeter, measure the voltage from the positive battery post to the negative battery post. It should read over 13.5 volts with the engine running. If it doesn’t read that much measure from the output post on the back of the alternator to the negative battery post. That should also read over 13.5 volts.

If your 2 measurements aren’t exactly the same you’ve got a failed fusible link or broken wire between the alternator and the battery.

yes the battery is brand new and no i did not get the charging system checked.

 I would not assume that either, even though you just bought them, or good.  Check each one along with all the connections.  Also you may want to check for some unusual load on the system?  

Hint: a battery cable may look fine and still have an internal defect, especially after messing with it when replacing a battery or alternator.

on the alternator there should be three wired one that is bolted on and goes to the battery. then the 2 in the plug. take a test light and check them 2 both with the key off then with the key in the on position they both should have power with it in the on position. The 1 that is bolted will be a constant hot.