Car Battery Problems...

[cracked]

hey yall. my car suddenly stop working right the other day. the battery will not charge. it is a brand new battery (3 weeks old). i thought that maybe the battery was bad so i put in another one that i know to be good and it still wont charge. i figured it was the alternator but if i jump the car off, it runs perfectly. it is only when i cut it off that it wil not even turn the engine over. could it still be the alternator? im no expert so please give me some davice

thanks!

drew

[caddmannq]

If the alternator's bad, the headlights won't get brighter as you rev up the engine.

It should read almost 14 volts at the battery, at about 1500 RPM. Got a voltmeter? ($12 at Walmart)

[cracked]

the meter that is above the gas guage is in the red (8) even with it running but as i said it runs fine once you get it started.

drew

Sounds like an alternator problem to me. Does your battery light come on when the car is running?

Check all your wires before you go buy something though, just in case.

[caddmannq]

It runs fine without an alternator, until the battery falls really low. Far below what's actually required to start the car.

Then it'll quit running.

But don't necessarilly trust the voltmeter on the dash.

Check the voltage right at the battery with a known-good meter.

Should be ~12.5 with the car off & ~13.8 running at 1500 RPM.

[fritz the cat]

Try this quick test, get the engine running, then disconnect the battery cables. If the engine dies, the alternator isn't working. If the engine still runs, post back and we'll go from there.

[SpookyEddy]

Stick a volt meter across the battery, when the car is at just off idle and the battery is being charged properly it should sit at about 14V. Hitting the gas should see a small increase in voltage and conversely loading it up (lights and heated rear window etc) may see a bit of a dip. Make sure that the battery is getting a good 13V+ even when fully loaded.

If the battery seems to be getting a good ~14V for a prolonged period of time but is still not holding charge then it is probably on the way out, you can take it to a garage and get it tested.

Regards

eddy

[Mike]

Do you have experience with this sort of thing Eddy?

[SpookyEddy]

Yeah I spent 3 weeks talking to G about why my car kept breaking down

<edit>changing my alternator cost me about £20 and took all of 20 minutes and some mild swearing</edit>

[Mike]

Ahhh well it happens.
Especially with your car it seems. At least pops didn't charge you for this "car" ..