Help! Can keeps dying..

[paperclip]

So after long drives or whatever, my car won't crank.
I thought it was the battery so I got a new battery. It helped for a little, but now my car is having the same problem.. I have to jump it every time.
Any thoughts?

[deutschman]

Check alternator. If its not recharging the battery it will die.
I cant help with your can problem however.

[E30_Pare]

+1 alternator dying. Should pull that new batt out before it get damaged, by how it sounds tho maybe to late for it.

[paperclip]

I tested my alternator.
My car still runs when the battery is disconnected.
Any other thoughts?

[E30_Pare]

yes but are you getting 14volts when running.

[jlevie]

The alternator can make enough power to run the engine, but not enough to keep the battery charged. Most likely the brushes in the alternator are worn out. They can be replaced and that makes the most sense if the alternator bearings are good.

Running the engine on just the alternator w/o the battery is dangerous to the electronics in the car. The battery acts as a filter to absorb spikes and noise.

[AndrewBird]

^^^What he said.

Check voltage at the battery with the car running. Should be somewhere around 14v. Battery should be at least 12.5v with the engine off.

Charge the battery fully out of the car before driving more. Using the alternator to charge the battery from dead can overload it and kill it. Might be what happened in your case. A bad battery killed your alternator.