here's the problem:

Car is driven for the first time in about 3 weeks. It's driven for maybe 10 min. 15 min later the car won't start. I jumped it and let it run for about 10 min and then went to drive it. I no more than backed it out of the parking spot and it died on me.

at first I thought bad Battery but now I'm thinking alternator....

any Ideas?

1/1/2006 5:01:33 PM

Yeah, I'm thinking you should have told us what kind of car you have. Sometimes there are known issues with certain cars that aren't even a remote problem with others.

But the symptoms definitely hint that the alternator could be at fault.

1/1/2006 5:34:40 PM

would measuring the voltage across the battery tell him if it's shot? should be ~14ish right?

1/1/2006 10:12:52 PM

Yep...anything between 13.5 and 14.5 or so should be fine.

1/1/2006 10:34:01 PM

a battery can be bad and still show ok voltage with no load

1/1/2006 11:42:59 PM

A good way to check the alternator is start the car.. then unhook the battery, if the car dies the alternator is probably bad. The best way is with a volt metter. Check the voltage with the car off, should be around 12 volts. Then crank the car, if the alternator is good it should read around 14 volts.

1/2/2006 12:16:34 AM

Quote :

"A good way to check the alternator is start the car.. then unhook the battery, if the car dies the alternator is probably bad."

This is nothing more than a good way to fry your ECM...voltage transients do NOT bode well for computer circuitry.

Quote :

"a battery can be bad and still show ok voltage with no load"

Sure it can. But a battery won't show between 13.5 and 14.5 volts...PERIOD. The big deal here is determining whether or not the alternator is putting out anything, which I'll bet it isn't.

True, the only surefire way to test a battery is load testing...the newest methods use dynamic load/recovery time testing.

1/2/2006 12:20:24 AM