well i changed my alternator a month ago and just changed my battery last week and my car was charging up fine i could see at the voltage meter that it was charging. but now it is not and my car just runs on the battery. i did the alternator test where you take off one of the post and the car should stay on if the alternator is fine, then immidiatly i get a response that the alternator is kicking agiain so i put back the battery post. and it charges fine after that till my destination. what could be the problem?

 

Maybe wiring. I replaced my wire from the alternator to the head main retractor thingy and then to the battery.

 

there is a wiring harness/connector that goes in the back of the alternator maybe that is unplugged, thats what happened with me once.

 

Put a multi meter on the posts, you should see around 12.5V with the car off, and around 13.5 to 14 with the car running.

You could have bad battery cables. They werent that great when they were new, and now they are around 20 years old.

 

I would suggest adding a ground wire too. From the negative battery post to the alternator bracket, it can't hurt and it might help.

 

I too had this problem! Symptom of this is that none of your warning lights in the dash will come on when you turn ignition to on.... well at least in my car