2003 Pontiac Montana Put New Alternator On Still Wont Charge Drains Battery

You need a multi meter so we can trouble shoot the problem. Here is a guide to help with the problem.

https://www.2carpros.com/articles/how-to-check-a-car-alternator

You need to check the wiring

https://www.2carpros.com/articles/how-to-check-wiring

Here is the alternator wiring harness (below) make sure you check the alternator fuse.

There is a red wire going to terminal B+ the one with a nut on there should be battery voltage there at the alternator. Also the orange wire to the D terminal at the alternator should have battery voltage. Let me know what you find?

Check out the diagrams (Below)

Please run this test and get back to us.

Cheers

now have multimeter

Lets start with the engine idling what is the voltage reading at the battery?

11.90 so I checked the wiring like you said and found the wire had pulled out the the connector once I fixed it the alternator is changing ya! I love this site.

Use 2CarPros anytime, we are here to help. Please tell a friend.

Cheers, Ken