My son left my door open on my 1995 Blazer LS 4WD, and it drained my battery, but I only had to jump it after it sat overnight. I got a new one and same thing the nxt morning. Took it back, it tested bad. The replacement has worked fine for several wks until last night. My battery light came on and the guage showed about half the amps it norm does, and my headlights were dimmer than normal, even though they had seemd dim to me for a few mths already. I drove it bout 15 mins, turned it off then about hlf hr later started heading home. After I took off, my lights went noticeably dim and after driving approx 10-15 mins my lights seemed to all go pretty much out and my battery amp guage basically dropped as I watched it. Once it got down past the orange almost to 0 line, I couldnt tell my headlights wer evn on... it started spittin n sputterin lik i was outa gas, it started sounding lik it needed to change gears when I was already doin over 50, and then it died. It took a jump fairly quick, but only long enuf to driv bout 20 ft. The nxt 2 jumps didnt evn last long enuf to get the cables off and my hood shut. I have no lights whatsoever yet they work if jumper cables are hooked up and Im getn power frm another battery. I think my alternator has been my prob sinc my 1st battery, so does the "runnin outta gas syndrome" sound like a symptom of an alternator finally quitting? And also would the alternator goin completely out make it suddenly whine like it is n the wrong gear before it dies? I never had either things happen before so I assume its a sign of the bad alternator.

 

Mel, I'm pretty sure your dash gauge is in volts, not amps. Volts equated to water is like pressure, amps is like flow. {gallons per minute etc}
The magic number is 12 because it's a twelve volt battery. If the needle is above twelve, current is flowing into the battery, below that, current is flowing out of the battery. The alternator, then, is like the city well pump keeping the water tower full, thus providing the pressure that creates the flow.
- When you turn the faucet and leave it running at the same time the pump runs, the water coming out is probably directly from the well not the tower. If the pump is broken, it's all coming from the tower.

Again, if the needle shows less than twelve you are draining the battery. Like the water, the more you run it, the lower the pressure/voltage gets till it's empty.

At the least your alternator is bad {or a wire is disconnected or broken}. Your battery may ALSO be bad. Put it this way, though... if your truck was running at all with the needle below 8, it's pretty healthy, otherwise.

 

LOL Ur right, it is in volts not amps (natural blonde here so I do apologize LOL) and it was the alternator that went out. I had to get a new battery (again!) though cause when I had returned the last one the guy at autozone stripped the threads when he put it in, so even if I had charged the battery bak up there was no way to tighten up the battery cables. I also had the alternator tested before I purchased a new one and it was in fact the issue, and where the dude stripped the threads on the battery for me they had to give me a replacement battery since it was still under warranty. So now I have a brand new alternator and a brand new battery and it is running at approx 14 volts now with no problems. I learned though that when the battery light comes on, I better find somewhere REALLLLY close by to park it cause I aint got much time before it dies and Im stranded. And I learned all about how the alternator and battery work and how they work together as well LOL