I little background:
On Sunday I was taking the family home from friends when I noticed the battery light on. I figured the battery was getting low so I planned on getting a new one on Monday. On Monday, I was taking the boy to day care and noticed the battery light was still on but I also noticed a surge in the engine while at idle to be more speciffice, when I was not putting a load on the gas peddle it would return to idle and than dip hard below the idle range. It would catch itself but was happinging more than I would like. I left the car running while I went in to drop him off when i came back out I noticed the interior clock light was out and now the abs light came on. On the way home, less than a mile away from day care the rest of the inteior lights went and the front lights started to go. By the time I pulled in front of the house the lights were all out and the car died.

I installed a new battery today and started it up to let the computer reset itself. The battery light is still on. Will this reset over time or coule my alt. be gone and I am only running on battery?

Chris

 

Definitely, a problem in your charging system. Go get your alt tested. I believe autozone tests them for free. Then comes the fun part of finding out why the alt is bad. They rarely go bad on their own. One piece of the puzzle has been replaced, so you'll never know if the old battery was the culprit.

 

Your alternator is bad. If you make it home to read this before you drain your new battery I will be supprised. Your truck was relying solely on the battery to get its power from. No juice, no spark, no run......Simple as that. Replace the alternator and you will be back in business.

 

Yep, it's the alternator. I second what FrmBoyBuck said. The power comes from the battery and the battery is recharged by the alternator while running, so if powered things slowly fade out, the battery is not being recharged enough to keep them going and ends up totally drained.

 

Who cares why it's bad? If it isn't charging, it isn't charging.

If you mean they rarely go bad in the sense that a winding breaks, or an armature cracks in half, true, not very often. If, however, you are referring to regulators, brushes or diodes crapping out as "going bad on their own", that happens all the time. Those three are the main reason alternators fail a bench test.

SL

 

I just wanted to update you all. I had the Alt changed yesterday and it seems to be running smooth again. thanks for all your help and advice.

Chris

 

My point being was that there are more things involved than just an alternator. For instance, if a battery has a bad cell, the alternator didn't go out on it's own, it overworked itself to death. Replacing the alternator would just buy you more time until the "weak" battery killed the new alternator (Since the battery was replaced already, it could've very well been the true cause). Or, another example would be corroded battery cables and/or the connections at the battery. The alternator would soon go out again if the true cause of the problem weren't corrected.

I'm not picking a fight, but trying to use this forum to educate myself and others, and, in the process, using my own experiences and knowledge to help people not only fix, but understand why things happen. --Tex

 

I understand your point as far as more than one thing being involved in the charging system, but the original post stated that the vehicle started up just fine, but the light was on. If if starts, you can rule out a bad cell, corroded cables and/or connections at the battery. Any of these can present a problem, but they will show up as starting problems long before a charging system problem. Or simplified, START=Large amount of amps going out, CHARGE=Much smaller amount of amps going back in. The connections, cables and bad cells will all prevent the flow of amps to spin the starter BEFORE they will prevent the alternator from charging the battery.
A battery with a bad cell will never cause the alternator to overwork itself to death unless the operator decides to jumpstart it everytime he drives. You could however have a bad ground from the alternator to the engine (mounting point), which can drastically reduce the voltage reaching the battery, which makes it look like your battery and alternator have both crapped out, when neither is really to blame. Did that help or make it worse?

SL

 

That was a very informative answer. Thanks. Sometimes it's easier, especially on a forum with all different experience levels, to just give an answer, but in your last reply you did a fair amount of deductive reasoning. It's nice to see the elimination process as you went through it in your head. I think others got something out of it as well. Now, when someone else has a similar problem, they can work through the same process and feel comfortable about the conclusion instead of just going off someone's answer off the internet. (Sorry, but I'm a "gotta know why it went bad", and "make everything a learning experience" type of guy.) Have a nice weekend.--tex