Why wont new alternator charge new battery on 68 dodge

Check all the electrical connections . grounds and to starter. One of them are bad or the new starter crapped out on you. Remember just because it is new doesn't mean it is good. I have got new items that were junk out of the box.

First, a bad battery doesn't turn the light on. Just A bad alternator or ECM. Start the car. put a volt meter on the + and - sides of the battery. If it reads 12 to 15 volts (closer to 15 for a new alternator). The alternator is good. And is charging. The problem is the wiring or the ECM. It can be bypassed to turn the light off. I just did it a week ago. Problem is , I don't have the wiring diagram for your car. Don't get a book from the parts store, it won't tell you. Go to alldata or Mitchell and purchase a manual. It's online and lasts a year. But they give you good electrical schematics...

The light is telling you the battery is low on charge. What you need to do is check the alternator and see if it is putting out the correct amperage. If you go to Auto zone they can check this for you and I believe it is free. Another test you could do is start the car and pull the positive cable from the battery and if the car dies then you have a charging problem and most likely is the alternator. A couple things about the battery itself. Make sure the connections are clean and tight. If the alternator is good then maybe the battery is not taking the charge from the alternator.

It could be a couple things. Take it to a shop or a place like auto zone and have them test the alternator and the battery, its free :) If they both are testing as good, the next thing would be to check the battery terminals and connections. It simply is not getting the enough charge back to the battery for one reason or another.

Try your headlights. If they are real dim or don't come on at all, the battery is dead. Since the battery is new, I would think the alternator is not charging the battery while the engine is running, You can have the alternator checked,

It could be the alternator not charging properly. Even though you're not having trouble starting the car, the alternator could be putting out just enough to handle charging the battery. But eventually it will go out. The battery light can mean either the battery is not charging correct from the alternator, or it's time to test the battery, which I think is good from your entry.

THE BATTERY LIGHT COMES ON TO ALERT YOU TO THE FACT THAT THE BATTERY IS NOT BEING CHARGED BY THE ALTERNATOR, IT DOESN'T MEAN THE BATTERY HAS A PROBLEM, HAVE THE ALTERNATOR TESTED FOR PROPER OPERATION.

With a volt meter and the engine at idle, check the voltage at the battery.It should always be just over 12 up to 14 volts. At idle with no accessorys on (lights, fan, radio ect.) The voltage should stay just over 12 volts. As you turn on all the accessorys the voltage should rise up to between 12-14 volts.
Also, a new battery needs to be fully charge before use. Most new batterys sit on the shelf and lose charge. My last new battery needed 8 hours of chargeing to be fully charged.
I hope this helps.

I am guessing that you put in a new battery drove it for a day at most and went out the next day and it wont start. Well if this is true then you will need an alternator, your battery is not being charged. Your car can start a run without this but you wouldn't get that far and eazy way to figure this out is either charge your battery or have a friend jump, be sure to let it charge for 3-5 min. before trying to start.
If it starts than remove the jumper cables and let the car tun for another 2-3 min and turn it off. If you cant restart it than you will need a new alternator