I'm So Lost.... battery won't hold charge.

[tboshearz]

So my 5.0's battery went dead so I figured it was just a bad battery.. got a new battery and it killed it again... so I get a new alternator...battery dies again... take the alternator back and get a new one... it tests out good on the bench test at autozone so we put a new one back in the car and it shows that no volts are going back to the battery from the alternator.

I know people get bad alternators from time to time but I've exchanged this one and had it tested along with the old one and they both tested out fine.

If I leave it sit I can start it up in the morning and drive it a block or so and the battery light comes on and the lights start dimming and then all power is gone...

So I understand that for some reason the alternator isn't getting power back to the battery and that's why it's dying.. but if the alternator is good what else could it be??

I'm so lost.. any help is appreciated.

 

[HISSIN50]

What voltage do you see when you start the car? Then when the battery light comes on?

If it takes a little bit for the light to illuminate, the alt might have a heat related issue, and thus it passes a bench test.

If you have a means of having it jump started, you can have the parts store do a dynamic charging system test (best to do it while the battery light is on, or the alt seems to not be doing all it can).

 

[tboshearz]

What voltage do you see when you start the car? Then when the battery light comes on?

If it takes a little bit for the light to illuminate, the alt might have a heat related issue, and thus it passes a bench test.

If you have a means of having it jump started, you can have the parts store do a dynamic charging system test (best to do it while the battery light is on, or the alt seems to not be doing all it can).

When I start the car the voltage will immediately drop to about 11 volts and then drop like a rock within a minute all the way down to 7 or 8 and that's when the car just loses all power and dies on me.

When they hooked the machine up to the alternator while the car was running it showed the alternator wasn't pushing any voltage out of itself... basically the only thing keeping the car on was the other battery we were using to jump it.

I just can't figure out why the alternator won't release any voltage back to the battery.

 

[ID89GT]

Is it the stock alternator or did you do the 3g swap

 

[HISSIN50]

With the car running, Check voltage at the back of the alt (the two charge wires on a 2G or the charge stud on a 3G) and compare it to the battery voltage.

You might have blown the circuit protection for the charge cable.

Otherwise, on your regulator plug, the A terminal should show battery voltage at all times, give or take a tenth of a volt or so.
The I terminal will show 1+ volts.
The S terminal should show about 1/2 battery voltage.

Good luck.