2007 Honda Civic battery light
 

I was driving my car and it quit running right after the battery light came on in the car. I replaced the alternator and the car ran fine. Light went out and drove for over an hour back home. The next day the light started coming on randomly and going out. I seem to have good power but it just comes on and goes out. I noticed today that if it came on and I turned on the AC it would go out and stay out. What do I need to check. Thanks for any ideas.

Welcome in,next take it to a auto zone and have the battery checked,it could have a bad cell,let them check the alt also ,I have bought and installed them and they last a few hours or maybe a day. You just don't know.

i took it to both auto zone and advance. Advance said the alternator and the other said the battery. I always seem to have this kind of luck.

Since involving the AC changes how the alternator works, I would take a look at the drive belts and make sure they're on tight. If it's not an issue with routing, maybe check the belt tensioner. If it's too loose, it could only work intermittently--here's a diagram that might help
ALTERNATOR BRACKET. Fits: 2007 Honda Civic | Honda Parts 2GO

Are you hearing any steady or intermittent belt squealing?

The belt does not make any noise. I got a third opinion and he told me the alternator was bad so I changed it and the car is still doing the same thing. The belt is tight and it does not make any noise. The light will come on but if I turn the air on it will go out , the wipers and lights seem fine. The battery is not old but I am thinking about replacing it unless someone has a better idea. My dad keeps telling me it is usually the opposite in that when the ac and other things are turned on the light would come on so he is thinking I should replace battery. The third opinion came from a mechanic and not auto or advance. I watched him test the other alternator and when we turn everything on the charge dropped so he felt pretty certain it was the alternator. I bet the odds of getting two bad alternators and the car doing the same are pretty low.

Have them do a drawdown test on the battery now that you have a new alt.

The battery light is pretty misleading, but it only comes on when the alternator output is below battery voltage, meaning it's not charging. If two alternators are having the same symptom, check to make sure the wire harness plugging into the alt is ok--not loose or burned--and that the contact on the bolted on wire is good with no corrosion. See the two things I'm talking about on this example pic:http://www.dahkee.com/Templates/pic/...TA7091-002.jpg

If they're fine, I'd really check to make sure the belt isn't flopping around too much when the a/c is on, indicating a bad belt tensioner.

Also, here's a pic of the tensioner and pulley for you to refer to:
ENGINE MOUNTING BRACKET (2.0L). Fits: 2007 Honda Civic | MagAuto Honda Parts