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2000 Eclipse -- battery not charging, recently replaced alternator

First off, as much as I enjoy listening to Car Talk, I am not, nor will I ever have the knowledge to do repairs myself (although I’m open to suggestions.)

I acquired a 2000 Eclipse from a friend of mine. Within 24 hours of having the car, it died, and I got a jump. Went to get the battery tested, the charge was around 55% and the guy told me that he could not test the alternator because the battery tested bad, but he got out a multimeter and told me that it was only outputting around 12v, and said that was all he could do.

The battery was brand new (replaced just before I got the car), and the alternator was replaced in January or February according to the previous owner.

I’ve been able to take the battery out and throw it on a charger, but for what it’s worth the terminals on the car are in very poor shape. Rusted out and seem very “finicky”, even if they are installed nice and tight, sometimes it still won’t supply power to the car and I have to adjust them. Obviously this might indicate that replacing the terminals would solve my issues, however, the alternator output should test fine then, yes?

So, there’s my situation. If anyone can make any suggestions, or maybe just tell me what I’m in for, that would be awesome.

before messing with the alternator you can try cleaning the batter post really good as well as the battery cable ends. This will ensure you are getting good contact.

If you have a simple volt meter you can test the alternator yourself. With the car running and all accessories off it should read somewhere between about 13.5 and 15.5

I don’t have a meter handy, but the guy at AutoZone said it was only outputting around 12v.

It does sound like the alternator may have an issue. Make sure the battery warning light tunrs on in the test mode as it may be part of the alternator circuit. There might be some bad diodes inside the alternator and that would help explain the low voltage level. You should replace the bad connections so that won’t be a possible issue. So many car problems are just due to bad battery connections. You don’t want to go there. Get a load test done on the system. Winter is coming and it will find any possible problems if there are any.