Is this the sign of a dead battery?

[Ribbedroof]

Since the car is down, and nobody is open anyway, this is a good time to pull the alt and take it with you to have it tested when you go for the new battery.

I think if you just replace the battery, you're going to be doing this again soon.

As mentioned above, trying to charge a dead/near dead battery with an alternator is hard on them. they are not designed to be used as a battery charger, their purpose is to supply electricity to the car, and "top off" the battery charge that was depleted by the starter motor.

 

[LukeZ]

don't overlook the alternator, bring that in to have it checked out

Sure thing, thanks

 

[pontiacgp]

Sure thing, thanks

if the alternator turns up defective then like axisg suggested find a local shop that rebuilds them and get one off of them using yours as a core. The shops build them better and stand behind their work, plus you can get one that puts out more amps than a more expensive store bought one

 

[Gozer442]

Clean and reseat all your connections too. A few dirty/loose connections can make for one big headache. In my experience, the battery and alternator are linked in lifespan, and can cause each other to malfunction. If either one goes, replace both. A new battery can be damaged by a faulty alternator, and it goes both ways...

 

[Opie Knievel]

I think you've got a bad battery and a bad alternator. You've tested the battery and you know it's bad. When you pulled the battery cable off with the car running and the car died, that means the alternator isn't charging enough to keep the car running. It takes less energy to run the car than to start it. That's why when you get a jump start the car fires up and runs, the jump provides enough amps to turn the starter. When you unhook the jumper cables, the car runs on the battery. It doesn't take a lot of amps to fire the spark plugs. I've had to carry a spare battery in my car before to get to a parts store to buy a new alternator. As long as you're not using the headlights, heater or other high amp accessories, a battery will run a car for a fairly long time. If you've got EFI, the length of time is shorter because of the fuel pump. The other guys are right that the alternator can be damaged by trying to charge a battery that's too dead.

Let us know what you find but my guess is that you'll be replacing both.

 

[axisg]

Clean and reseat all your connections too. A few dirty/loose connections can make for one big headache. In my experience, the battery and alternator are linked in lifespan, and can cause each other to malfunction. If either one goes, replace both. A new battery can be damaged by a faulty alternator, and it goes both ways...

that is what I was alluding to. A bad cell in the battery will overheat the windings in the alternator in fairly short order as it will always be in a state of trying to fully charge the battery. This will lead to the death of a good alternator.

Its money well spent to replace both as others have said.