I have heard about this on the other forum that I posted on. This past Saturday I didn't have any problems taking off the connector terminal and it showed no corrosion. I would I check to see if the post is broken inside the battery?

 

I had that problem on my original battery the positive post started to break off the battery and it was giving me some funky readings off the alternator. I would still think its the alternator even though you took it and they said it was ok. But check the post might that might be good luck.

 

i was thinking bad rectifier on alternator

 

What is that? The rectifier, not the alternator.

 

The alternator actually produces AC voltage... The rectifier converts that to your 12 (14 actually) volts, DC. I think they're all internal to the alternators these days. If there is a rebuild kit for your (our?) alternators, I think it usually includes the rectifier... (usually just a few diodes if I remember right)

 

Been there done that. If you have and AC Delco, it's only a matter of time before this problem happens anyway. What happens is the contact heats up inside the battery causing it to separate. Sometimes you can't tell it is broken since it happens from the inside. They don't always leak either. I'd pull the battery if you haven't and look under it for corrosion. That's where I found my evidence. The post was clean, but it leaked down to the batt pan.

 

To me, it definitely sounds like a charging system problem. If you think of the gauge as in two parts... 0-12V, and then from 12 to about 14.5V... the battery handles the 0-12 range, and the charging system (what I just referred to as the alternator before) handles the 12-14.5 range...

If the 12-14 range isn't working, the battery isn't getting a charge... It could be the alternator, or something internal to it like the rectifier like Keuka mentioned... Then it could be the "hot" wire coming off the alternator. (I think it's a 8 or 10 gauge wire bolted to the alternator. It should have a protective rubber sleeve over the mounting lug. It's possible (but not real likely) that it's badly corroded or loose....

To directly check the alternators output - with the engine running, just toss a volt meter's black lead on the engine block or valve cover or something, and with the motor running, put the red lead on that lug - if you're still seeing 12V, the alternator is not putting the power out. If you see ~14 or so - there is an issue from that wire to the rest of the electical system... (I think the wires goes to the fuse box from there). Maybe something internal with the battery like mentioned above...

 

One thing I should mention that I found very odd.

My ex girlfriend had a Hyundai (sp?). One day the battery was dead. We jumped the car, and I started poking at things with my volt-meter. There was no power coming out of the alternator. I though, "okay, piece of cake, get a new one."

We spend somewhere around $350 (!!!!!!) for a rebuilt one. I don't know what was so special about it.

I bolted it up, started the car and still - nothing out the alternator. "WTF."

I stopped by a Hyund-whatever delership, and found out that the alternator needs to see a certain voltage from the battery before it will decide to start putting power out. This thing was only seeing like, 11.75 after the jump. It was still nearly dead.

I thought that this was the dumbest thing ever, but figured I'd give it a whirl. I put the cars battery on a charger overnight. I connected it back up with like 12.5V, and sure enough we started the car and the alternator was working.

I put in the original alternator, and was able to return the expensive one.

It turned out that she was leaving her cell-phone charger plugged in while the car was parked. The cig-lighters in that car were live all the time, so it was constantly draining the battery. That's how it went dead - after a certain voltage, the alternator (allegedly) decided "enough is enough" and didn't put power out.

Now I **REALLY** don't think these GM's are designed like this, but it wouldn't hurt to put the battery on a charger for the night and see how the battery gauge responds the next day or two.

 

Thanks everybody for the replies. I think I will replace the battery that I have now, since I have been hearing a lot of stories about the AC Delco batteries going bad. I will post up if everything goes back to normal or stays the same. Thanks again.

 

You might also want to go ahead and replace the 8 guage wire from the Alternator to the "Hot" box that leads from the battery. That is the box where they suggest to place the hot jumper cable on. I have heard that the 8 gauge wire that leads from the box to the alternator is sometimes not enough. Many of the guys here have gone ahead and swapped it out with 4 guage wire or larger. This might not make much of a difference, but the wire is only a few bucks at the auto parts and it definitely wouldn't hurt.