Okay, I'll try to keep this as short as possible, even though I doubt it will be short at all. Sorry.

My Battery gauge has been fluctuating a lot, I tried to figure it out before, but never got anywhere. I checked at the battery with a multimeter, the voltage was around 11.3-11.6 at idle, majorly discharged. Battery before a start up is sitting at about 12.1, a little discharged from what I've read.

I remembered hearing somewhere that if you pull the negative battery cable with the car running it should continue to run, I also read that it's a good way to kill your alternator. But I figured since I got a problem, it can't hurt me much more, so I pulled the cable with it running, it kept running, but not very well, it started to surge a bit, the engine would bog down, then come back, each time seeming to bog down a bit more. I got the bright idea of watching the volts with a multimeter when it was doing this.

They were bounching 2+ volts, from 13.5 to 11.5 and sometimes a little lower or higher, completely dependent on the surge.

I then shut the car off, and reconnected the battery, started it up, and checked the volts, right around 11.3 at idle. Surging was gone with the battery hooked up again. So I might have put a lot of stress on my alternator, but something seems wrong here.

I then checked connections, first the charging lug on the back of the alternator, cleaned it, checked resistance between the wire and the positive side of the battery, close to no resistance. Hooked it back up, checked voltage with car off, within .08 volts from battery cable to alternator lug. I then cleaned both sides of the battery, and the battery itself, shined everything up and connected it all tightly.

I then tested, same results as earlier. It seems the alternator is putting out something, just not enough. When it's cold out, my volts don't come up with RPMs, not by much anyways, maybe up to 12.5, but when warm outside, I approach 13.3 volts at speed (2000 RPMs or so)

I took my car to Sears and they said the battery is bad. But wasn't sure of the alternator, said they couldn't check with the bad battery. My question is, did my alternator kill the battery, or did the battery just go bad. It is a DieHard Gold, just over 3 years old... seems it should still be good.

I put my charger on the battery today at about 5:30pm, it was taking 6 amps at the beginning, it dropped to 4 amps after 3 1/2 hours, and right now it's down to 2.25 amps, after 5 hours 45 minutes, seems like it might be taking a charge, but I don't know if it will hold it.

All ground straps are intact and in good condition also. What's going on here, is my alternator bad, along with the battery?

I've got a new Optima Red Top on it's way (98.70 shipped off eBay). I'm afriad to put it in tho, cause I don't wanna ruin another battery if my alternator is bad.

Help me guys... any other ideas, or input is appreciated. Thanks!

 

You have already found your problem I think. I would take the alternator to the parts store that can check. Any time the engine is running, you should have near to14 volts,(13.8-14.2) charging on a 12 volt battery. Good Luck

 

So did that mean you think it's the battery, or the alternator? I took the alternator to a parts store about 2 months ago (when this problem started getting more noticeable) and they said it tested fine, I watched them test it, and the Machine said Pass.

 

One thing that hasn't been mentioned and it may or not have any bearing on the problem. Have you checked the belt tension on the fan belt lately?

 

It's pretty tight...

I may sound like an idiot, but how tight should it be ideally?

I don't think it's slipping.

 

The basic tension that should be on the belt is between 103 - 127 pounds with A/C. Shop technicians use a special gage to measure the tension on the belt. Usually a rule of thumb is that if you can put your thumb on the belt and deflect it by roughly 1/2" while pressing down it is too loose. Look at the range marking on the belt tensioner and see where the arrow is located.

 

Not serpantine, it's an 87. The AC and Powersteering is V-belt, the alternator/waterpump is a wider belt, I guess it's called serpantine, but just on the Alt and Water Pump. So less than 1/2 inch deflection.. it's good.

 

I'm no Trickster, he's in 501 land(good). But, start the process of elimination IMHO. The alt. acts like the culprit, might want to try a different Parts Store. Auto Parts = Here today, gone tomorrow, at least satisfy or not alt. Good Luck

 

Sorry Dude,

The tension on your alternator belt should be 135 LBS. new and 90 LBS. used. BTW, "used" refers to the belt completing one full revolution on the engine pulleys. This begins the seating process of the belt and the belt should never be reset to "new" belt specifications.

 

I believe my belt is fine. I notice, even with the weak battery, that my volts bounce around, up and down randomly, without any change in RPMs...

Like I said the car started surging bad when running off just the alternator, I watched the volts then and they dropped and recovered just like the engine. It seems like the alternator is weak, and it just doesn't put out much power here and there, like it's output surges... but is this just because of the bad battery?

I'm thinking of replacing it, just to be safe... think that's a good idea?