91 Camaro RS with 305 TBI. I have replaced the battery, altenator, positive and neg battery cables. I ran great for a month and now the battery goes dead. The altenator is putting out 14.5 volts and is charging the battery but the battery will be dead in 20 minutes. Please help anyone.

 

Does it go dead 20 mins after sitting? I thlnk I would have the battery tested if not you have something drawing a lot of current while it is shut off. Have do a amp draw down on it.

 

The battery goes dead 20 minutes after I shut the car off. There is no amp in the car. I noticed the altenator makes a humming noise when I shut the car off.

 

He's not talking about an audio amp. An amp draw is a test where you place a multi meter inline with the battery cable (between the possitive post and the cable). In your case, there will be a load on the battery. Start pulling fuses, when the meter drops to zero (indicating the draw is gone) check that circuit.

I have had alternators that would drain the battery when sitting. Not sure it was 20min fast though. If yours is making any noises, I'd look at replacing it. Just because it's new (or more likely re-manufactured) does not mean it is working correctly.

 

Did not mean to confuse you .I would take battery and alternator and battery insince alt is making noise could have bad cell in battery put pressure on idler pulley make sure belt is tight.

 

sounds like you have a bad diode in your alternator or a ground in the armature