2000 Suburban Battery Problems

I have a 2000 Suburban with about 220,000 miles on it. I hadn't driven it for about two weeks and went out to start it and it started right up. I did notice that the battery light was on but as I said, it started right up so figured maybe it would go out after it ran for a while. After running at idle for about 5 minutes, I noticed a sudden decrease in engine speed and noticed the dash lights were dimming and suddenly the engine died. When I attempted to start it, the battery was dead. I jumped it and it ran for a minute and died again. I figured maybe the battery was toast so I took it in to Autozone as a warranty since it's less than two years old. They "tested" it and said that the battery is good and suggested that the problem was elsewhere. They did charge it up and I put it in the vehicle and it started right up but the battery light is still on and volt gauge is showing about 11-12 volts. One other thing to mention that I noticed for the past year or so, is that when I'm driving at night I notice the headlights and dash lights dim slightly when I'm accelerating hard. Not sure if that has anything to do with it though. Appreciate any help.

test your alternator.

when the red battery lamp is on , the alternator is not charging. 14volts is what a voltmeter should read at the battery engine on.13volts or less is a bad alternator. just to add to the vehicle you own , this vehicle under normal operation requires 65AMPS .. so no alternator the battery will die quickly. if this is the OEM 16 yr old alternator I would say your very lucky because these had defective regulators that the circuit would corrode. I would buy a new NOT rebuilt alternator that's what I did 10 yrs ago. AZ should have this under a lifetime warranty as my alternator is.

Ok thanks very much for the feedback. Sounds like I need to look at the alternator. One other thing to mention is that when the engine is running, the battery light comes on and goes off intermittently and there is no pattern to this.

test your alternator.
Thanks for the suggestion. I'll give that a shot.

Thanks for the suggestion. I'll give that a shot.

the issue you have is what I had ... the alternator regulator is with corrosion and causes the lights to dim intermittently then the red battery light comes on..

I had to take 2 weeks to finally nail it down on testing because it was so intermittent. I have all the testing tools to check this out and it did get worse so I made sure not to spend $175 for a new alternator .. my alternator failed @120K miles ..

You can replace the internal voltage regulator your self if you have the tools.

You can replace the internal voltage regulator your self if you have the tools.

I actually tried to find this and also opened up the alternator it is not all that easy .. this is not built like a old style alternator.. same with the starters made today hard to find rebuild parts. not many do this so no availability.

because of the delay to do this , I just got the new one with a lifetime warranty.